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Evaluating Research – Process, Examples and Methods

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Evaluating Research

Definition:

Evaluating Research refers to the process of assessing the quality, credibility, and relevance of a research study or project. This involves examining the methods, data, and results of the research in order to determine its validity, reliability, and usefulness. Evaluating research can be done by both experts and non-experts in the field, and involves critical thinking, analysis, and interpretation of the research findings.

Research Evaluating Process

The process of evaluating research typically involves the following steps:

Identify the Research Question

The first step in evaluating research is to identify the research question or problem that the study is addressing. This will help you to determine whether the study is relevant to your needs.

Assess the Study Design

The study design refers to the methodology used to conduct the research. You should assess whether the study design is appropriate for the research question and whether it is likely to produce reliable and valid results.

Evaluate the Sample

The sample refers to the group of participants or subjects who are included in the study. You should evaluate whether the sample size is adequate and whether the participants are representative of the population under study.

Review the Data Collection Methods

You should review the data collection methods used in the study to ensure that they are valid and reliable. This includes assessing the measures used to collect data and the procedures used to collect data.

Examine the Statistical Analysis

Statistical analysis refers to the methods used to analyze the data. You should examine whether the statistical analysis is appropriate for the research question and whether it is likely to produce valid and reliable results.

Assess the Conclusions

You should evaluate whether the data support the conclusions drawn from the study and whether they are relevant to the research question.

Consider the Limitations

Finally, you should consider the limitations of the study, including any potential biases or confounding factors that may have influenced the results.

Evaluating Research Methods

Evaluating Research Methods are as follows:

• Peer review: Peer review is a process where experts in the field review a study before it is published. This helps ensure that the study is accurate, valid, and relevant to the field.
• Critical appraisal : Critical appraisal involves systematically evaluating a study based on specific criteria. This helps assess the quality of the study and the reliability of the findings.
• Replication : Replication involves repeating a study to test the validity and reliability of the findings. This can help identify any errors or biases in the original study.
• Meta-analysis : Meta-analysis is a statistical method that combines the results of multiple studies to provide a more comprehensive understanding of a particular topic. This can help identify patterns or inconsistencies across studies.
• Consultation with experts : Consulting with experts in the field can provide valuable insights into the quality and relevance of a study. Experts can also help identify potential limitations or biases in the study.
• Review of funding sources: Examining the funding sources of a study can help identify any potential conflicts of interest or biases that may have influenced the study design or interpretation of results.

Example of Evaluating Research

Example of Evaluating Research sample for students:

Title of the Study: The Effects of Social Media Use on Mental Health among College Students

Sample Size: 500 college students

Sampling Technique : Convenience sampling

• Sample Size: The sample size of 500 college students is a moderate sample size, which could be considered representative of the college student population. However, it would be more representative if the sample size was larger, or if a random sampling technique was used.
• Sampling Technique : Convenience sampling is a non-probability sampling technique, which means that the sample may not be representative of the population. This technique may introduce bias into the study since the participants are self-selected and may not be representative of the entire college student population. Therefore, the results of this study may not be generalizable to other populations.
• Participant Characteristics: The study does not provide any information about the demographic characteristics of the participants, such as age, gender, race, or socioeconomic status. This information is important because social media use and mental health may vary among different demographic groups.
• Data Collection Method: The study used a self-administered survey to collect data. Self-administered surveys may be subject to response bias and may not accurately reflect participants’ actual behaviors and experiences.
• Data Analysis: The study used descriptive statistics and regression analysis to analyze the data. Descriptive statistics provide a summary of the data, while regression analysis is used to examine the relationship between two or more variables. However, the study did not provide information about the statistical significance of the results or the effect sizes.

Overall, while the study provides some insights into the relationship between social media use and mental health among college students, the use of a convenience sampling technique and the lack of information about participant characteristics limit the generalizability of the findings. In addition, the use of self-administered surveys may introduce bias into the study, and the lack of information about the statistical significance of the results limits the interpretation of the findings.

Note*: Above mentioned example is just a sample for students. Do not copy and paste directly into your assignment. Kindly do your own research for academic purposes.

Applications of Evaluating Research

Here are some of the applications of evaluating research:

• Identifying reliable sources : By evaluating research, researchers, students, and other professionals can identify the most reliable sources of information to use in their work. They can determine the quality of research studies, including the methodology, sample size, data analysis, and conclusions.
• Validating findings: Evaluating research can help to validate findings from previous studies. By examining the methodology and results of a study, researchers can determine if the findings are reliable and if they can be used to inform future research.
• Identifying knowledge gaps: Evaluating research can also help to identify gaps in current knowledge. By examining the existing literature on a topic, researchers can determine areas where more research is needed, and they can design studies to address these gaps.
• Improving research quality : Evaluating research can help to improve the quality of future research. By examining the strengths and weaknesses of previous studies, researchers can design better studies and avoid common pitfalls.
• Informing policy and decision-making : Evaluating research is crucial in informing policy and decision-making in many fields. By examining the evidence base for a particular issue, policymakers can make informed decisions that are supported by the best available evidence.
• Enhancing education : Evaluating research is essential in enhancing education. Educators can use research findings to improve teaching methods, curriculum development, and student outcomes.

Purpose of Evaluating Research

Here are some of the key purposes of evaluating research:

• Determine the reliability and validity of research findings : By evaluating research, researchers can determine the quality of the study design, data collection, and analysis. They can determine whether the findings are reliable, valid, and generalizable to other populations.
• Identify the strengths and weaknesses of research studies: Evaluating research helps to identify the strengths and weaknesses of research studies, including potential biases, confounding factors, and limitations. This information can help researchers to design better studies in the future.
• Inform evidence-based decision-making: Evaluating research is crucial in informing evidence-based decision-making in many fields, including healthcare, education, and public policy. Policymakers, educators, and clinicians rely on research evidence to make informed decisions.
• Identify research gaps : By evaluating research, researchers can identify gaps in the existing literature and design studies to address these gaps. This process can help to advance knowledge and improve the quality of research in a particular field.
• Ensure research ethics and integrity : Evaluating research helps to ensure that research studies are conducted ethically and with integrity. Researchers must adhere to ethical guidelines to protect the welfare and rights of study participants and to maintain the trust of the public.

Characteristics Evaluating Research

Characteristics Evaluating Research are as follows:

• Research question/hypothesis: A good research question or hypothesis should be clear, concise, and well-defined. It should address a significant problem or issue in the field and be grounded in relevant theory or prior research.
• Study design: The research design should be appropriate for answering the research question and be clearly described in the study. The study design should also minimize bias and confounding variables.
• Sampling : The sample should be representative of the population of interest and the sampling method should be appropriate for the research question and study design.
• Data collection : The data collection methods should be reliable and valid, and the data should be accurately recorded and analyzed.
• Results : The results should be presented clearly and accurately, and the statistical analysis should be appropriate for the research question and study design.
• Interpretation of results : The interpretation of the results should be based on the data and not influenced by personal biases or preconceptions.
• Generalizability: The study findings should be generalizable to the population of interest and relevant to other settings or contexts.
• Contribution to the field : The study should make a significant contribution to the field and advance our understanding of the research question or issue.

Advantages of Evaluating Research

Evaluating research has several advantages, including:

• Ensuring accuracy and validity : By evaluating research, we can ensure that the research is accurate, valid, and reliable. This ensures that the findings are trustworthy and can be used to inform decision-making.
• Identifying gaps in knowledge : Evaluating research can help identify gaps in knowledge and areas where further research is needed. This can guide future research and help build a stronger evidence base.
• Promoting critical thinking: Evaluating research requires critical thinking skills, which can be applied in other areas of life. By evaluating research, individuals can develop their critical thinking skills and become more discerning consumers of information.
• Improving the quality of research : Evaluating research can help improve the quality of research by identifying areas where improvements can be made. This can lead to more rigorous research methods and better-quality research.
• Informing decision-making: By evaluating research, we can make informed decisions based on the evidence. This is particularly important in fields such as medicine and public health, where decisions can have significant consequences.
• Advancing the field : Evaluating research can help advance the field by identifying new research questions and areas of inquiry. This can lead to the development of new theories and the refinement of existing ones.

Limitations of Evaluating Research

Limitations of Evaluating Research are as follows:

• Time-consuming: Evaluating research can be time-consuming, particularly if the study is complex or requires specialized knowledge. This can be a barrier for individuals who are not experts in the field or who have limited time.
• Subjectivity : Evaluating research can be subjective, as different individuals may have different interpretations of the same study. This can lead to inconsistencies in the evaluation process and make it difficult to compare studies.
• Limited generalizability: The findings of a study may not be generalizable to other populations or contexts. This limits the usefulness of the study and may make it difficult to apply the findings to other settings.
• Publication bias: Research that does not find significant results may be less likely to be published, which can create a bias in the published literature. This can limit the amount of information available for evaluation.
• Lack of transparency: Some studies may not provide enough detail about their methods or results, making it difficult to evaluate their quality or validity.
• Funding bias : Research funded by particular organizations or industries may be biased towards the interests of the funder. This can influence the study design, methods, and interpretation of results.

About the author

Muhammad Hassan

Researcher, Academic Writer, Web developer

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1 Important points to consider when critically evaluating published research papers

Simple review articles (also referred to as ‘narrative’ or ‘selective’ reviews), systematic reviews and meta-analyses provide rapid overviews and ‘snapshots’ of progress made within a field, summarising a given topic or research area. They can serve as useful guides, or as current and comprehensive ‘sources’ of information, and can act as a point of reference to relevant primary research studies within a given scientific area. Narrative or systematic reviews are often used as a first step towards a more detailed investigation of a topic or a specific enquiry (a hypothesis or research question), or to establish critical awareness of a rapidly-moving field (you will be required to demonstrate this as part of an assignment, an essay or a dissertation at postgraduate level).

The majority of primary ‘empirical’ research papers essentially follow the same structure (abbreviated here as IMRAD). There is a section on Introduction, followed by the Methods, then the Results, which includes figures and tables showing data described in the paper, and a Discussion. The paper typically ends with a Conclusion, and References and Acknowledgements sections.

The Title of the paper provides a concise first impression. The Abstract follows the basic structure of the extended article. It provides an ‘accessible’ and concise summary of the aims, methods, results and conclusions. The Introduction provides useful background information and context, and typically outlines the aims and objectives of the study. The Abstract can serve as a useful summary of the paper, presenting the purpose, scope and major findings. However, simply reading the abstract alone is not a substitute for critically reading the whole article. To really get a good understanding and to be able to critically evaluate a research study, it is necessary to read on.

While most research papers follow the above format, variations do exist. For example, the results and discussion sections may be combined. In some journals the materials and methods may follow the discussion, and in two of the most widely read journals, Science and Nature, the format does vary from the above due to restrictions on the length of articles. In addition, there may be supporting documents that accompany a paper, including supplementary materials such as supporting data, tables, figures, videos and so on. There may also be commentaries or editorials associated with a topical research paper, which provide an overview or critique of the study being presented.

Box 1 Key questions to ask when appraising a research paper

• Is the study’s research question relevant?
• Does the study add anything new to current knowledge and understanding?
• Does the study test a stated hypothesis?
• Is the design of the study appropriate to the research question?
• Do the study methods address key potential sources of bias?
• Were suitable ‘controls’ included in the study?
• Were the statistical analyses appropriate and applied correctly?
• Is there a clear statement of findings?
• Does the data support the authors’ conclusions?
• Are there any conflicts of interest or ethical concerns?

There are various strategies used in reading a scientific research paper, and one of these is to start with the title and the abstract, then look at the figures and tables, and move on to the introduction, before turning to the results and discussion, and finally, interrogating the methods.

Another strategy (outlined below) is to begin with the abstract and then the discussion, take a look at the methods, and then the results section (including any relevant tables and figures), before moving on to look more closely at the discussion and, finally, the conclusion. You should choose a strategy that works best for you. However, asking the ‘right’ questions is a central feature of critical appraisal, as with any enquiry, so where should you begin? Here are some critical questions to consider when evaluating a research paper.

Look at the Abstract and then the Discussion : Are these accessible and of general relevance or are they detailed, with far-reaching conclusions? Is it clear why the study was undertaken? Why are the conclusions important? Does the study add anything new to current knowledge and understanding? The reasons why a particular study design or statistical method were chosen should also be clear from reading a research paper. What is the research question being asked? Does the study test a stated hypothesis? Is the design of the study appropriate to the research question? Have the authors considered the limitations of their study and have they discussed these in context?

Take a look at the Methods : Were there any practical difficulties that could have compromised the study or its implementation? Were these considered in the protocol? Were there any missing values and, if so, was the number of missing values too large to permit meaningful analysis? Was the number of samples (cases or participants) too small to establish meaningful significance? Do the study methods address key potential sources of bias? Were suitable ‘controls’ included in the study? If controls are missing or not appropriate to the study design, we cannot be confident that the results really show what is happening in an experiment. Were the statistical analyses appropriate and applied correctly? Do the authors point out the limitations of methods or tests used? Were the methods referenced and described in sufficient detail for others to repeat or extend the study?

Take a look at the Results section and relevant tables and figures : Is there a clear statement of findings? Were the results expected? Do they make sense? What data supports them? Do the tables and figures clearly describe the data (highlighting trends etc.)? Try to distinguish between what the data show and what the authors say they show (i.e. their interpretation).

Moving on to look in greater depth at the Discussion and Conclusion : Are the results discussed in relation to similar (previous) studies? Do the authors indulge in excessive speculation? Are limitations of the study adequately addressed? Were the objectives of the study met and the hypothesis supported or refuted (and is a clear explanation provided)? Does the data support the authors’ conclusions? Maybe there is only one experiment to support a point. More often, several different experiments or approaches combine to support a particular conclusion. A rule of thumb here is that if multiple approaches and multiple lines of evidence from different directions are presented, and all point to the same conclusion, then the conclusions are more credible. But do question all assumptions. Identify any implicit or hidden assumptions that the authors may have used when interpreting their data. Be wary of data that is mixed up with interpretation and speculation! Remember, just because it is published, does not mean that it is right.

O ther points you should consider when evaluating a research paper : Are there any financial, ethical or other conflicts of interest associated with the study, its authors and sponsors? Are there ethical concerns with the study itself? Looking at the references, consider if the authors have preferentially cited their own previous publications (i.e. needlessly), and whether the list of references are recent (ensuring that the analysis is up-to-date). Finally, from a practical perspective, you should move beyond the text of a research paper, talk to your peers about it, consult available commentaries, online links to references and other external sources to help clarify any aspects you don’t understand.

The above can be taken as a general guide to help you begin to critically evaluate a scientific research paper, but only in the broadest sense. Do bear in mind that the way that research evidence is critiqued will also differ slightly according to the type of study being appraised, whether observational or experimental, and each study will have additional aspects that would need to be evaluated separately. For criteria recommended for the evaluation of qualitative research papers, see the article by Mildred Blaxter (1996), available online. Details are in the References.

Activity 1 Critical appraisal of a scientific research paper

A critical appraisal checklist, which you can download via the link below, can act as a useful tool to help you to interrogate research papers. The checklist is divided into four sections, broadly covering:

• some general aspects
• research design and methodology
• the results
• discussion, conclusion and references.

Science perspective – critical appraisal checklist [ Tip: hold Ctrl and click a link to open it in a new tab. ( Hide tip ) ]

• Identify and obtain a research article based on a topic of your own choosing, using a search engine such as Google Scholar or PubMed (for example).
• The selection criteria for your target paper are as follows: the article must be an open access primary research paper (not a review) containing empirical data, published in the last 2–3 years, and preferably no more than 5–6 pages in length.
• Critically evaluate the research paper using the checklist provided, making notes on the key points and your overall impression.

Critical appraisal checklists are useful tools to help assess the quality of a study. Assessment of various factors, including the importance of the research question, the design and methodology of a study, the validity of the results and their usefulness (application or relevance), the legitimacy of the conclusions, and any potential conflicts of interest, are an important part of the critical appraisal process. Limitations and further improvements can then be considered.

Evaluating Research Articles

Understanding research statistics, critical appraisal, help us improve the libguide.

Imagine for a moment that you are trying to answer a clinical (PICO) question regarding one of your patients/clients. Do you know how to determine if a research study is of high quality? Can you tell if it is applicable to your question? In evidence based practice, there are many things to look for in an article that will reveal its quality and relevance. This guide is a collection of resources and activities that will help you learn how to evaluate articles efficiently and accurately.

Is health research new to you? Or perhaps you're a little out of practice with reading it? The following questions will help illuminate an article's strengths or shortcomings. Ask them of yourself as you are reading an article:

• Is the article peer reviewed?
• Are there any conflicts of interest based on the author's affiliation or the funding source of the research?
• Are the research questions or objectives clearly defined?
• Is the study a systematic review or meta analysis?
• Is the study design appropriate for the research question?
• Is the sample size justified? Do the authors explain how it is representative of the wider population?
• Do the researchers describe the setting of data collection?
• Does the paper clearly describe the measurements used?
• Did the researchers use appropriate statistical measures?
• Are the research questions or objectives answered?
• Did the researchers account for confounding factors?
• Have the researchers only drawn conclusions about the groups represented in the research?
• Have the authors declared any conflicts of interest?

If the answer to these questions about an article you are reading are mostly YESes , then it's likely that the article is of decent quality. If the answers are most NOs , then it may be a good idea to move on to another article. If the YESes and NOs are roughly even, you'll have to decide for yourself if the article is good enough quality for you. Some factors, like a poor literature review, are not as important as the researchers neglecting to describe the measurements they used. As you read more research, you'll be able to more easily identify research that is well done vs. that which is not well done.

Determining if a research study has used appropriate statistical measures is one of the most critical and difficult steps in evaluating an article. The following links are great, quick resources for helping to better understand how to use statistics in health research.

• How to read a paper: Statistics for the non-statistician. II: “Significant” relations and their pitfalls This article continues the checklist of questions that will help you to appraise the statistical validity of a paper. Greenhalgh Trisha. How to read a paper: Statistics for the non-statistician. II: “Significant” relations and their pitfalls BMJ 1997; 315 :422 *On the PMC PDF, you need to scroll past the first article to get to this one.*
• A consumer's guide to subgroup analysis The extent to which a clinician should believe and act on the results of subgroup analyses of data from randomized trials or meta-analyses is controversial. Guidelines are provided in this paper for making these decisions.

Statistical Versus Clinical Significance

When appraising studies, it's important to consider both the clinical and statistical significance of the research. This video offers a quick explanation of why.

If you have a little more time, this video explores statistical and clinical significance in more detail, including examples of how to calculate an effect size.

• Statistical vs. Clinical Significance Transcript Transcript document for the Statistical vs. Clinical Significance video.
• Effect Size Transcript Transcript document for the Effect Size video.
• P Values, Statistical Significance & Clinical Significance This handout also explains clinical and statistical significance.
• Absolute versus relative risk – making sense of media stories Understanding the difference between relative and absolute risk is essential to understanding statistical tests commonly found in research articles.

Critical appraisal is the process of systematically evaluating research using established and transparent methods. In critical appraisal, health professionals use validated checklists/worksheets as tools to guide their assessment of the research. It is a more advanced way of evaluating research than the more basic method explained above. To learn more about critical appraisal or to access critical appraisal tools, visit the websites below.

• Last Updated: Jun 11, 2024 10:26 AM
• URL: https://libguides.massgeneral.org/evaluatingarticles

• University Libraries
• Research Guides
• Critical Evaluation

Authority: Critical Evaluation

• World Views and Voices
• Understanding Peer Review

Critical Evaluation of Information Sources

After initial evaluation of a source, the next step is to go deeper. This includes a wide variety of techniques and may depend on the type of source. In the case of research, it will include evaluating the methodology used in the study and requires you to have knowledge of those discipline-specific methods. If you are just beginning your academic career or just entered a new field, you will likely need to learn more about the methodologies used in order to fully understand and evaluate this part of a study.

Lateral reading is a technique that can, and should, be applied to any source type. In the case of a research study, looking for the older articles that influenced the one you selected can give you a better understanding of the issues and context. Reading articles that were published after can give you an idea of how scholars are pushing that research to the next step. This can also help with understanding how scholars engage with each other in conversation through research and even how the academic system privileges certain voices and established authorities in the conversation. You might find articles that respond directly to studies that provide insight into evaluation and critique within that discipline.

Evaluation at this level is central to developing a better understanding of your own research question by learning from these scholarly conversations and how authority is tested.

Check out the resources below to help you with this stage of evaluation.

Scientific Method/Methodologies

Here is a general overview of how the scientific method works and how scholars evaluate their work using critical thinking. This same process is used when scholars write up their scholarly work. 

The Steps of the Scientific Method

Question something that was observed, do background research to better understand, formulate a hypothesis (research question), create an experiment or method for studying the question, run the experiment and record the results, think critically about what the results mean, suggest conclusions and report back, lateral reading.

Critical Thinking

Thinking critically about the information you encounter is central to how you develop your own conclusions, judgement, and position. This analysis is what will allow you to make a valuable contribution of your own to the scholarly conversation.

• TEDEd: Dig Deeper on the 5 Tips to Improve Your Critical Thinking
• The Foundation for Critical Thinking: College and University Students
• Stanford Encyclopedia of Philosophy: Critical Thinking

Scholarship as Conversation

It sounds pretty bad if you say an article was retracted, but is it always? As with most things, it depends on the context. Someone retracting a statement made based on false information or misinformation is one thing. It happens fairly often in the case of social media--removed tweets or Instagram posts for example.

In scholarship, there are a number of reasons an article might be retracted. These range from errors in the methods used, experiment structure, data, etc. to issues of fraud or misrepresentation. Central to scholarship is the community of scholars actively participating in the scholarly conversation even after the peer review process. Careful analysis of published research by other scholars is vital to course correction.

In science research, it's a central part of the process ! An inherent part of discovery is basing conclusions on the information at hand and repeating the process to gather more information. If further research is done that provides new information and insight, that might mean an older conclusion gets corrected. Uncertainty is unsettling, but trust in the process means understanding the important role of retraction.

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• Review Article
• Published: 20 January 2009

How to critically appraise an article

• Jane M Young 1 &
• Michael J Solomon 2  

Nature Clinical Practice Gastroenterology & Hepatology volume  6 ,  pages 82–91 ( 2009 ) Cite this article

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Critical appraisal is a systematic process used to identify the strengths and weaknesses of a research article in order to assess the usefulness and validity of research findings. The most important components of a critical appraisal are an evaluation of the appropriateness of the study design for the research question and a careful assessment of the key methodological features of this design. Other factors that also should be considered include the suitability of the statistical methods used and their subsequent interpretation, potential conflicts of interest and the relevance of the research to one's own practice. This Review presents a 10-step guide to critical appraisal that aims to assist clinicians to identify the most relevant high-quality studies available to guide their clinical practice.

Critical appraisal is a systematic process used to identify the strengths and weaknesses of a research article

Critical appraisal provides a basis for decisions on whether to use the results of a study in clinical practice

Different study designs are prone to various sources of systematic bias

Design-specific, critical-appraisal checklists are useful tools to help assess study quality

Assessments of other factors, including the importance of the research question, the appropriateness of statistical analysis, the legitimacy of conclusions and potential conflicts of interest are an important part of the critical appraisal process

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JM Young is an Associate Professor of Public Health and the Executive Director of the Surgical Outcomes Research Centre at the University of Sydney and Sydney South-West Area Health Service, Sydney,

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MJ Solomon is Head of the Surgical Outcomes Research Centre and Director of Colorectal Research at the University of Sydney and Sydney South-West Area Health Service, Sydney, Australia.,

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Young, J., Solomon, M. How to critically appraise an article. Nat Rev Gastroenterol Hepatol 6 , 82–91 (2009). https://doi.org/10.1038/ncpgasthep1331

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Critically appraising qualitative research

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• Peer review
• Ayelet Kuper , assistant professor 1 ,
• Lorelei Lingard , associate professor 2 ,
• Wendy Levinson , Sir John and Lady Eaton professor and chair 3
• 1 Department of Medicine, Sunnybrook Health Sciences Centre, and Wilson Centre for Research in Education, University of Toronto, 2075 Bayview Avenue, Room HG 08, Toronto, ON, Canada M4N 3M5
• 2 Department of Paediatrics and Wilson Centre for Research in Education, University of Toronto and SickKids Learning Institute; BMO Financial Group Professor in Health Professions Education Research, University Health Network, 200 Elizabeth Street, Eaton South 1-565, Toronto
• 3 Department of Medicine, Sunnybrook Health Sciences Centre
• Correspondence to: A Kuper ayelet94{at}post.harvard.edu

Six key questions will help readers to assess qualitative research

Summary points

Appraising qualitative research is different from appraising quantitative research

Qualitative research papers should show appropriate sampling, data collection, and data analysis

Transferability of qualitative research depends on context and may be enhanced by using theory

Ethics in qualitative research goes beyond review boards’ requirements to involve complex issues of confidentiality, reflexivity, and power

Over the past decade, readers of medical journals have gained skills in critically appraising studies to determine whether the results can be trusted and applied to their own practice settings. Criteria have been designed to assess studies that use quantitative methods, and these are now in common use.

In this article we offer guidance for readers on how to assess a study that uses qualitative research methods by providing six key questions to ask when reading qualitative research (box 1). However, the thorough assessment of qualitative research is an interpretive act and requires informed reflective thought rather than the simple application of a scoring system.

Box 1 Key questions to ask when reading qualitative research studies

Was the sample used in the study appropriate to its research question.

Were the data collected appropriately?

Were the data analysed appropriately?

Can I transfer the results of this study to my own setting?

Does the study adequately address potential ethical issues, including reflexivity?

Overall: is what the researchers did clear?

One of the critical decisions in a qualitative study is whom or what to include in the sample—whom to interview, whom to observe, what texts to analyse. An understanding that qualitative research is based in experience and in the construction of meaning, combined with the specific research question, should guide the sampling process. For example, a study of the experience of survivors of domestic violence that examined their reasons for not seeking help from healthcare providers might focus on interviewing a …

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Critically Analyzing Information Sources: Critical Appraisal and Analysis

• Critical Appraisal and Analysis

Initial Appraisal : Reviewing the source

• What are the author's credentials--institutional affiliation (where he or she works), educational background, past writings, or experience? Is the book or article written on a topic in the author's area of expertise? You can use the various Who's Who publications for the U.S. and other countries and for specific subjects and the biographical information located in the publication itself to help determine the author's affiliation and credentials.
• Has your instructor mentioned this author? Have you seen the author's name cited in other sources or bibliographies? Respected authors are cited frequently by other scholars. For this reason, always note those names that appear in many different sources.
• Is the author associated with a reputable institution or organization? What are the basic values or goals of the organization or institution?

B. Date of Publication

• When was the source published? This date is often located on the face of the title page below the name of the publisher. If it is not there, look for the copyright date on the reverse of the title page. On Web pages, the date of the last revision is usually at the bottom of the home page, sometimes every page.
• Is the source current or out-of-date for your topic? Topic areas of continuing and rapid development, such as the sciences, demand more current information. On the other hand, topics in the humanities often require material that was written many years ago. At the other extreme, some news sources on the Web now note the hour and minute that articles are posted on their site.

C. Edition or Revision

Is this a first edition of this publication or not? Further editions indicate a source has been revised and updated to reflect changes in knowledge, include omissions, and harmonize with its intended reader's needs. Also, many printings or editions may indicate that the work has become a standard source in the area and is reliable. If you are using a Web source, do the pages indicate revision dates?

D. Publisher

Note the publisher. If the source is published by a university press, it is likely to be scholarly. Although the fact that the publisher is reputable does not necessarily guarantee quality, it does show that the publisher may have high regard for the source being published.

E. Title of Journal

Is this a scholarly or a popular journal? This distinction is important because it indicates different levels of complexity in conveying ideas. If you need help in determining the type of journal, see Distinguishing Scholarly from Non-Scholarly Periodicals . Or you may wish to check your journal title in the latest edition of Katz's Magazines for Libraries (Olin Reference Z 6941 .K21, shelved at the reference desk) for a brief evaluative description.

Critical Analysis of the Content

Having made an initial appraisal, you should now examine the body of the source. Read the preface to determine the author's intentions for the book. Scan the table of contents and the index to get a broad overview of the material it covers. Note whether bibliographies are included. Read the chapters that specifically address your topic. Reading the article abstract and scanning the table of contents of a journal or magazine issue is also useful. As with books, the presence and quality of a bibliography at the end of the article may reflect the care with which the authors have prepared their work.

A. Intended Audience

What type of audience is the author addressing? Is the publication aimed at a specialized or a general audience? Is this source too elementary, too technical, too advanced, or just right for your needs?

B. Objective Reasoning

• Is the information covered fact, opinion, or propaganda? It is not always easy to separate fact from opinion. Facts can usually be verified; opinions, though they may be based on factual information, evolve from the interpretation of facts. Skilled writers can make you think their interpretations are facts.
• Does the information appear to be valid and well-researched, or is it questionable and unsupported by evidence? Assumptions should be reasonable. Note errors or omissions.
• Are the ideas and arguments advanced more or less in line with other works you have read on the same topic? The more radically an author departs from the views of others in the same field, the more carefully and critically you should scrutinize his or her ideas.
• Is the author's point of view objective and impartial? Is the language free of emotion-arousing words and bias?

C. Coverage

• Does the work update other sources, substantiate other materials you have read, or add new information? Does it extensively or marginally cover your topic? You should explore enough sources to obtain a variety of viewpoints.
• Is the material primary or secondary in nature? Primary sources are the raw material of the research process. Secondary sources are based on primary sources. For example, if you were researching Konrad Adenauer's role in rebuilding West Germany after World War II, Adenauer's own writings would be one of many primary sources available on this topic. Others might include relevant government documents and contemporary German newspaper articles. Scholars use this primary material to help generate historical interpretations--a secondary source. Books, encyclopedia articles, and scholarly journal articles about Adenauer's role are considered secondary sources. In the sciences, journal articles and conference proceedings written by experimenters reporting the results of their research are primary documents. Choose both primary and secondary sources when you have the opportunity.

D. Writing Style

Is the publication organized logically? Are the main points clearly presented? Do you find the text easy to read, or is it stilted or choppy? Is the author's argument repetitive?

E. Evaluative Reviews

• Locate critical reviews of books in a reviewing source , such as the Articles & Full Text , Book Review Index , Book Review Digest, and ProQuest Research Library . Is the review positive? Is the book under review considered a valuable contribution to the field? Does the reviewer mention other books that might be better? If so, locate these sources for more information on your topic.
• Do the various reviewers agree on the value or attributes of the book or has it aroused controversy among the critics?
• For Web sites, consider consulting this evaluation source from UC Berkeley .

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How to critically evaluate the quality of a research article?

So what’s the criteria to determine whether a result can be trusted? As it is taught in the first classes in psychology, errors may emerge from any phase of the research process. Therefore, it all boils down to how the research has been conducted and the results presented.

Meltzoff (2007) emphasizes the key issues that can produce flawed results and interpretations and should therefore be carefully considered when reading articles. Here is a reminder on what to bear in mind when reading a research article:

Research question The research must be clear in informing the reader of its aims. Terms should be clearly defined, even more so if they’re new or used in specific non-spread ways. You as a reader should pay particular attention should to errors in logic, especially those regarding causation, relationship or association.

Sample To provide trustworthy conclusions, a sample needs to be representative and adequate. Representativeness depends on the method of selection as well as the assignment.  For example, random assignment has its advantages in front of systematic assignment in establishing group equivalence. The sample can be biased when researchers used volunteers or selective attrition. The adequate sample size can be determined by employing power analysis.

Control of confounding variables Extraneous variation can influence research findings, therefore methods to control  relevant confounding variables should be applied.

Research designs The research design should be suitable to answer the research question. Readers should distinguish true experimental designs with random assignment from pre-experimental research designs.

Criteria and criteria measures The criteria measures must demonstrate reliability and validity for both, the independent and dependent variable.

Data analysis Appropriate statistical tests should be applied for the type of data obtained, and assumptions for their use met. Post hoc tests should be applied when multiple comparisons are performed. Tables and figures should be clearly labelled. Ideally, effect sizes shou

ld be included throughout giving a clear indication of the variables’ impact.

Discussion and conclusions Does the study allow generalization? Also, limitations of the study should be mentioned. The discussion and conclusions should be consistent with the study’s results. It’s a common mistake to emphasizing the results that are in accordance with the researcher’s expectations while not focusing on the ones that are not. Do the authors of the article you hold in hand do the same?

Ethics Last but not least, ere the ethical standards met? For more information, refer to the APA’s Ethical Principles of Psychologists and Code of Conduct (2010).

References American Psychological Association (2010, June 1).  American Psychological Association Ethical Principles of Psychologists and Code of Conduct . Retrieved July 28, 2011 from  http://www.apa.org/ethics/code/index.aspx

Meltzoff, J. (2007). Critical Thinking About Research. Washington, DC: American Psychological Association.

Edited by: Maris Vainre

Zorana Zupan

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How to do library research: Critically Evaluate Information

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Critically Evaluate Information Links

Primary and secondary sources, common information source formats.

Critically evaluating sources using the CRAP Method

Uses of different types of sources

Evaluating web sources

What is a primary source?

A primary source is original information about an event, person, object, product, or work of art in which there has been no comment or analysis about it; a primary source presents information in its original form, neither interpreted nor condensed nor evaluated by other writers.

Think about it in your own context. What primary sources have you created to tell the story of you? (For example, maybe a tweet, a picture of something you enjoy doing, or your student ID card).

What is a secondary source? 

A secondary source is an interpretation of a primary source. For example, if your professor asks you to view a film and then write a paragraph about it's meaning to you, the film is the primary source, while your analysis of the film is the secondary source. 

What do we mean by “sources”?

Critically Evaluate Information

Critically Evaluating Sources ( what do we mean by "sources"? )

For college-level research, you'll want to consider using only the highest-quality information sources that you can find.  Between the internet and SU’s library, the “ best ” information can depend on the assignment. Here are some ways to determine the best information sources to lend support to your own research.

Use the C.R.A.P. method to evaluate information that you may consider using: (Currency, Relevance, Author expertise, and Purpose)

Bean, J. C. (2011). Designing and sequencing assignments to teach undergraduate research. In  Engaging ideas: The professor's guide to integrating writing, critical thinking, and active learning in the classroom  (2nd ed., p. 239). San Francisco: Jossey-Bass.

This information is an adaptation of Evaluating Information – Applying the CRAAP Test created by Meriam Library, CSU, Chico

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• Critical Evaluation of Sources
• Why Evaluate?

Critical Evaluation of Sources: Why Evaluate?

• Introduction and Criteria
• Web and Articles

While most of us realize that we can’t trust all the information we see or read, we don’t always spend a lot of time considering how we actually make decisions about what to trust. Whether we’re watching the news, reading a friend’s blog, researching a health condition, or using information in some other way, we generally draw on our own values and life experiences to make relatively quick judgments about the validity of the information we are exposed to or seek out. Sometimes we don’t even consider the fact that we made a judgment about what to trust in the first place. We’re simply on autopilot.

Although the amount of deep thinking we need to put into evaluating the validity of an information source can vary depending on the significance of the situation, we ultimately make better decisions and construct more convincing arguments when we have a strong understanding of the quality of the information we’re using (or not using). This is especially true in an academic context, where our ability to create knowledge and meaning depends on our ability to analyze and interpret information with precision.   

To evaluate information, then, is to analyze information from a critical perspective. The evaluative process requires us to step back and carefully consider the sources we use and how we use them, to not rush to judgment but to think through the content of the articles we’re reading or the online search results we’re browsing. We also need to consider the relationships among different sources and how they work together to form “conversations” around certain topics or issues. A “conversation” in this sense refers to the diverse perspectives and arguments surrounding a particular research question (or set of questions).

The questions in this guide can help you think through the evaluation of information sources. Keep in mind that evaluation is not simply about determining whether a source is “reliable” or “not reliable.” It’s rarely that easy or straightforward. Instead, it’s more useful to consider the degree to which a source is reliable for a given purpose.  The primary goal of evaluation is to understand the significance and value of a source in relation to other sources and your own thinking on a topic.

Note that some evaluative questions will be more important than others depending on your needs as a researcher. Figuring out which questions are important to ask in a given situation is part of the research process. Also note that your evaluation of a source may evolve over time. For instance, a source that seems very useful early on may prove less useful as your project develops. Likewise, a source that seems insignificant at the beginning of a project may turn out to be your most significant source later in the research process.

From:   http://louisville.libguides.com/evaluation

This evaluation process is really no different than the process people use everyday as they acquire all types of information from a neighbor, a friend, a newspaper, a television broadcast, or a bulletin board flyer. 

All of this happens so automatically, you don't even realize you're doing it. While you should evaluate all of information sources (books, periodical articles, etc.) before using them in your research, it is most vital that you evaluate the information you find on the Internet.  Every book and article published (even those available in Internet-based databases) goes through some sort of evaluation process, but Web pages go through no such pre-publication evaluation.

The number of resources available via the Internet is immense. Companies, organizations, educational institutions, communities and individual people all serve as information providers for the Internet community. Savvy members of the Internet community are aware that there are few, if any, quality controls for the information that is made available. Accurate and reliable data may share the computer screen with data that is inaccurate, unreliable, or even purposely false. In addition, the differences between the two types of data may be imperceptible, especially for someone who is not an expert in the topic area. Because the Internet is not the responsibility of any one organization or institution, it seems unlikely that any universal quality control will be established in the near future. In view of this, members of the Internet community must prepare themselves to be critically skilled consumers of the information they find.

Hoaxes, Fallacies, Propaganda - OH MY!

Types of hoaxes with examples -   http://virtualchase.justia.com/hoaxes-and-other-bad-information

Listing of Types of Fallacies  -  http://www.nizkor.org/features/fallacies/

Propaganda -    http://guides.library.jhu.edu/content.php?pid=198142&sid=1657614

Critical Thinkers

Characteristics of Critical Thinkers:   http://www.mhhe.com/socscience/philosophy/reichenbach/m1_chap02studyguide.html

Defining Critical Thinking

A Source:   http://www.criticalthinking.org/pages/defining-critical-thinking/766

Which states:  

The Problem  Everyone thinks; it is our nature to do so. But much of our thinking, left to itself, is biased, distorted, partial, uninformed or down-right prejudiced. Yet the quality of our life and that of what we produce, make, or build depends precisely on the quality of our thought. Shoddy thinking is costly, both in money and in quality of life. Excellence in thought, however, must be systematically cultivated.

A Definition  Critical thinking is that mode of thinking - about any subject, content, or problem - in which the thinker improves the quality of his or her thinking by skillfully taking charge of the structures inherent in thinking and  imposing intellectual standards upon them.

The Result  A well cultivated critical thinker:

• raises vital questions and problems, formulating them clearly and precisely;
• gathers and assesses relevant information, using abstract ideas to interpret it effectively  comes to well-reasoned conclusions and solutions, testing them against relevant criteria and standards;
• thinks openmindedly within alternative systems of thought, recognizing and assessing, as need be, their assumptions, implications, and practical consequences; and
• communicates effectively with others in figuring out solutions to complex problems.

Critical thinking is, in short, self-directed, self-disciplined, self-monitored, and self-corrective thinking. It presupposes assent to rigorous standards of excellence and mindful command of their use. It entails effective communication and problem solving abilities and a commitment to overcome our native egocentrism and sociocentrism.

Critical Thinking

Critical Thinking and introduction to the basic skills by William Hughes 1992 Broadview Press Ltd. Lewiston, NY Isbn 1-921149-73-2 The primary focus of critical thinking skills is on determining whether arguments are sound, i.e. whether they have true premises and logical strength.But determining the soundness of arguments is not a simple matter, for three reasons.First, before we can assess an argument we must determine its precise meaning. Second, determining the truth or falsity of statements is often a difficult task. Third, assessing argument is complex because there are several different types of inferences and each type requires a different kind of assessment.  There three types of skills—

interpretive skills, verification skills, and reason skills—constitutes what are usually referred to as critical thinking skills.  … mastering critical thinking skills is also a matter of intellectual self-respect.  We all have the capacity to learn how to distinguish good arguments from bad ones and to work out for ourselves what we ought and ought not to believe, and it diminishes us as persons if we let others do our thinking for us.  If we are not prepared to think for ourselves, and to make the effort to learn how do this well, we will always remain slaves to the ideas and values of others and to our own ignorance. P. 11 Argumentation and Debate Critical thinking for reasoned decision Making Austin J. Freeley and David L. Steinberg 10th edition 2000 Wadsworth/Thomson Learning Belmont, CA Isbn 0-534-46115-2

Critical thinking:   the ability to analyze, criticize, and advocate ideas; to reason inductively and deductively; and to reach factual or judgmental conclusions based on sound inferences drawn from unambiguous statements of knowledge or belief.    P. 458 Author: Theresa Rienzo, Reference Librarian,James Edward Tobin Library, Molloy College 1000 Hempstead Ave. Rockville Centre, NY  11571

Copied from:   http://molloy.libguides.com/criticalthinking

A critical thinking model with elements:   http://www.criticalthinking.org/ctmodel/logic-model1.htm

From:   http://www.edpsycinteractive.org/topics/cogsys/critthnk.html

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Oxidative stress and cataract formation: evaluating the efficacy of antioxidant therapies.

1. Introduction

2. the structure and physiology of the lens, physiology of the lens and its redox regulatory mechanisms, 3. ocular damages induced by reactive oxygen species: cataracto-genesis, 3.1. antioxidative systems, 3.2. protein aggregation, cross-linking, and light-scattering, 3.3. lipid peroxidation and loss of membrane integrity, 4. antioxidant strategies for the prevention and management of cataracts, 4.1. dietary nutrients and supplements, 4.1.1. vitamins c and e, 4.1.2. lutein and zeaxanthin, 4.2. potential pharmacological agents with antioxidative properties for cataract prevention and treatment, 4.2.1. n-acetyl-carnosine, 4.2.2. n-acetylcysteine amide, 4.2.3. resveratrol, 4.2.4. baicalein, 4.2.5. metformin, 4.3. nanotechnology-based drug delivery systems for cataract prevention and treatment, 4.3.1. n-acetylcarnosine nanoparticles, 4.3.2. resveratrol nanoparticles and nanovesicles, 4.3.3. baicalin, 4.3.4. cerium oxide, 4.4. gene therapy for cataract prevention and treatment, 4.4.1. suicide gene therapy, 4.4.2. rna interference, 4.4.3. crispr-cas9, 5. challenges and limitations of antioxidants and novel therapeutic approaches, 6. recommendations and future directions, 7. conclusions, author contributions, conflicts of interest.

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Kulbay, M.; Wu, K.Y.; Nirwal, G.K.; Bélanger, P.; Tran, S.D. Oxidative Stress and Cataract Formation: Evaluating the Efficacy of Antioxidant Therapies. Biomolecules 2024 , 14 , 1055. https://doi.org/10.3390/biom14091055

Kulbay M, Wu KY, Nirwal GK, Bélanger P, Tran SD. Oxidative Stress and Cataract Formation: Evaluating the Efficacy of Antioxidant Therapies. Biomolecules . 2024; 14(9):1055. https://doi.org/10.3390/biom14091055

Kulbay, Merve, Kevin Y. Wu, Gurleen K. Nirwal, Paul Bélanger, and Simon D. Tran. 2024. "Oxidative Stress and Cataract Formation: Evaluating the Efficacy of Antioxidant Therapies" Biomolecules 14, no. 9: 1055. https://doi.org/10.3390/biom14091055

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Levels of Evidence, Quality Assessment, and Risk of Bias: Evaluating the Internal Validity of Primary Research

Jan m. sargeant.

1 Department of Population Medicine, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada

Marnie L. Brennan

2 Centre for Evidence-Based Veterinary Medicine, School of Veterinary Medicine and Science, University of Nottingham, Sutton Bonington Campus, Loughborough, United Kingdom

Annette M. O'Connor

3 Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI, United States

Clinical decisions in human and veterinary medicine should be based on the best available evidence. The results of primary research are an important component of that evidence base. Regardless of whether assessing studies for clinical case management, developing clinical practice guidelines, or performing systematic reviews, evidence from primary research should be evaluated for internal validity i.e., whether the results are free from bias (reflect the truth). Three broad approaches to evaluating internal validity are available: evaluating the potential for bias in a body of literature based on the study designs employed (levels of evidence), evaluating whether key study design features associated with the potential for bias were employed (quality assessment), and applying a judgement as to whether design elements of a study were likely to result in biased results given the specific context of the study (risk of bias assessment). The level of evidence framework for assessing internal validity assumes that internal validity can be determined based on the study design alone, and thus makes the strongest assumptions. Risk of bias assessments involve an evaluation of the potential for bias in the context of a specific study, and thus involve the least assumptions about internal validity. Quality assessment sits somewhere between the assumptions of these two. Because risk of bias assessment involves the least assumptions, this approach should be used to assess internal validity where possible. However, risk of bias instruments are not available for all study designs, some clinical questions may be addressed using multiple study designs, and some instruments that include an evaluation of internal validity also include additional components (e.g., evaluation of comprehensiveness of reporting, assessments of feasibility or an evaluation of external validity). Therefore, it may be necessary to embed questions related to risk of bias within existing quality assessment instruments. In this article, we overview the approaches to evaluating internal validity, highlight the current complexities, and propose ideas for approaching assessments of internal validity.

Introduction

Every day in clinical practice, veterinary professionals need to make decisions ranging from a decision as to whether (or not) to use an intervention or to apply a diagnostic test, to decisions about the overall management of complex clinical conditions. Increasingly, it is expected that clinical decisions are evidence-based. Evidence-based veterinary medicine incorporates clinician experience, client preferences, animal needs, and scientific evidence when making clinical decisions ( 1 ). In this approach, scientific evidence is obtained from relevant research. When research-based evidence does not exist, other sources of evidence, such as expert opinion may need to be used. Traditional narrative reviews provide an overview of a topic, and thus may be an attractive way of quickly acquiring knowledge for making clinical decisions. However, narrative reviews generally do not provide information on the identification and selection of the primary research being summarized (if any), the methodological quality of the studies, or the magnitude of the expected effect ( 2 , 3 ).

Formal methods have been developed to systematically identify, select, and synthesize the available evidence to assist veterinary professionals in evidence-based decision-making. These include critically appraised topics (CATs) ( 4 ), systematic review and meta-analysis (SR-MA) ( 5 – 7 ), and clinical practice guidelines ( 8 ) (see Box 1 for a short overview of these methods). These evidence synthesis approaches have different purposes which results in different processes and endpoints, but each includes an assessment of the internal validity of the research used. Critical appraisal of an individual study also includes an evaluation of internal validity, in addition to an evaluation of feasibility and generalizability ( 10 ). The evaluation of internal validity is the focus of this article. Understanding the different ways internal validity can be assessed, and the assumptions associated with these approaches, is necessary for researchers evaluating internal validity, and for veterinary professionals to assess studies for integration of evidence into practice.

Overview of synthesis methods used in veterinary practice and research.

Systematic review, meta-analysis, and network meta-analysis: Systematic review is a structured methodology for identifying, selecting and evaluating all relevant research to address a structured question, which may relate to descriptive characteristics such as prevalence, etiology, efficacy of interventions, or diagnostic test accuracy ( 5 ). Meta-analysis is the statistical combination of results from multiple studies. For addressing questions on intervention efficacy, meta-analysis provides an overall effect size for pairwise comparisons between two intervention groups. Network meta-analysis allows an estimation of the comparative efficacy across all available intervention options ( 6 ), which may provide more relevant information for veterinary professionals when there are multiple intervention options available. However, systematic reviews with pairwise meta-analysis or network meta-analysis require that a body of research exists that can be synthesized to address a clinical question and can also be resource and time intensive to conduct. Therefore, there are many clinical questions for which formally synthesized research summaries do not exist.

Critically appraised topics: Critically appraised topics (CATs) use the same principles as systematic reviews to address clinical questions but employ a more rapid approach, particularly in relation to the screening and summation of the evidence. They were designed to be employed by clinicians as a way of rapidly gathering and interpreting evidence on clinical questions relating to specific cases ( 4 ). Therefore, there is a greater risk that research addressing the question may be missed. However, in the absence of a well conducted systematic review or meta-analysis, CATs can provide a faster evaluation of research addressing a clinical question and can be undertaken by veterinary professionals who may have fewer resources and potentially less methodological or statistical expertise, particularly if they are freely available and accessible.

Clinical practice guidelines: Veterinary professionals often are involved in the management of complex clinical conditions, where an array of questions need to be addressed, including those related to etiology, prognosis, diagnostic test accuracy, and intervention efficacy. Clinical practice guidelines are intended to assist healthcare professionals in assessing more than one aspect of case approach, including appropriate prevention, diagnosis, treatment, or clinical management of diseases, disorders, and other health conditions ( 9 ). Although there are differences in the methods among authors and institutions, the key elements of guideline development include the establishment of a multidisciplinary working group to develop the guidelines, the involvement of appropriate stakeholders, identification of the topic area, systematic searches for research evidence, assessment of the internal validity of studies comprising the evidence base, a process for drafting recommendations, and ongoing review and updating of the guidelines as new evidence becomes available ( 8 ).

Internal validity refers to the extent to which the study results reflect the true state of nature (i.e., whether the effect size estimated in a study is free from systematic error, also called bias) ( 11 ). Although there are a large number of named biases ( 12 ), for studies that assess interventions or risk factors, the biases can be categorized into three broad types of bias: selection bias, information bias, and confounding ( 13 ). Selection bias impacts the effect size if, compared to the source population, the exposure or intervention groups differ in the distribution of factors associated with the outcome at the time the study population is selected, or if differential loss to follow up between groups occurs during the study. In case-control studies, selection bias occurs if cases or controls are selected based on criteria that are related to the exposure of interest. Information bias occurs when there are errors in measuring the exposure or intervention, or the outcome, or both. Finally, confounding is a mixing of effects that occurs when a variable (the confounder) that is independently associated with both the exposure and the outcome is not properly controlled. When confounding is not controlled, the estimate of the relationship between the exposure and the outcome will be biased.

There are several terms used to describe the approaches to assessing internal validity of primary research studies, including evidence hierarchies and levels of evidence, quality assessment, and risk of bias assessment. The use of these terms may be confusing, and it is not uncommon for some of these terms to be used interchangeably ( 14 , 15 ). Also, authors may mislabel the approaches and some evaluation tools (instruments) available for assessing internal validity may include additional components, such as those related to comprehensiveness (quality) of reporting, feasibility of applying an intervention, or external validity. Finally, some instruments may use the approach as a label for the instrument [e.g., Cochrane's risk of bias tool ( 16 ), which is an instrument that employs a risk of bias approach] and other instruments may not include the approach in the instrument name [e.g., the Jadad scale ( 17 ), which employs a quality assessment approach]. In an evaluation of the comprehensiveness of reporting in animal health systematic reviews (SRs), Sargeant et al., ( 18 )found that a range of instruments involving all three approaches had been used for assessing the internal validity of primary research studies. Although a large number of instruments are available, the approaches within each instrument used to assess internal validity can be grouped into three broad categories: based on study design, based on the presence or absence of design features, or based on a judgement about bias in the context of the study. These categories generally correspond to levels of evidence, quality assessment, and risk of bias, respectively. Therefore, our objective was to review these approaches to assessing internal validity as distinct entities and to describe the assumptions associated with each approach. Although we provide examples of specific instruments that include an evaluation of internal validity, our focus is on the approaches, rather than the tools. We discuss advances in the use of these approaches to assessing internal validity in human healthcare and propose a process for veterinary medicine for selecting the approach with the least assumptions as appropriate to the clinical question, the purpose of the assessment, and the research found that addresses the question of interest. The target audience for this article is individuals who assess internal validity of studies, individuals who develop instruments that include items related to the assessment of internal validity, and those who use evidence synthesis products created by others, such as systematic reviews or clinical practice guidelines.

Evaluating Internal Validity by Study Design: Levels of Evidence

Levels of evidence is an approach to evaluating the internal validity of a body of evidence, based on the potential for bias which is inherent to the employed study designs that were used to address the clinical question. The concept behind levels of evidence is that there is a hierarchy of study designs, with different study designs having different potential for bias. The way evidence hierarchies are used is based on either the name of the design or the description of the design. Readers of a study look for this information, then determine the design and assign a level of evidence. No further differentiation of methodological features or judgment is conducted.

Evidence hierarchies were initially introduced in 1979 by the Canadian Task Force on the Periodic Health Examination ( 19 ), with further development into an evidence pyramid by David Sackett in 1989 ( 20 ). A pyramid shaped figure commonly is used to illustrate the hierarchy of study designs for evaluating the efficacy of an intervention under realistic-use conditions (owned animals, as opposed to experimental settings), with the potential for bias decreasing from the base to the top of the pyramid ( Figure 1 ). Thus, study designs on the top of the pyramid represent those with inherently lower risk of bias compared to study designs lower on the hierarchy. The pyramid shape acknowledges that the quantity of research tends to decrease in the higher levels of evidence (for instance, there will be a larger volume of randomized controlled trials (RCTs) compared to SR-MA). Suggested modifications to the evidence pyramid for veterinary intervention studies include dividing RCTs into those conducted under realistic-use conditions vs. those conducted in nonrealistic-use conditions (e.g., research facility) ( 21 ), the inclusion of challenge trials (where disease outcomes are deliberately induced) below RCTs in the pyramid ( 21 , 22 ), and increasing the interpretability of the concept for students by displaying the hierarchy as a staircase rather than a pyramid ( 23 ).

Illustration of an evidence pyramid hierarchy for addressing intervention studies in veterinary medicine. SR, systematic review; MA, meta-analysis; RCT, randomized controlled trial.

The concept of evaluating the potential for bias in an individual study based on the study design can be extended to an evaluation of the potential for bias in a body of literature. This approach for evaluating the internal validity of a body of literature is referred to as “levels of evidence”. The approach is applied by identifying research (or other evidence) that pertains to the clinical question, determining the study design used for each of the studies, and then assigning each study to a level of evidence based on that design. For instance, a framework for levels of evidence in veterinary clinical nutrition has been proposed by Roudebush et al. ( 24 ). In this framework, level 1 evidence corresponds to at least 1 appropriately designed RCT in the target species with natural disease development, level 2 evidence would correspond to RCTs in laboratory settings with natural disease development, level 3 evidence would be obtained from non-randomized trials, deliberate disease induction trials, analytical observational studies or case series, and level 4 evidence would correspond to expert opinion, descriptive studies, studies in other species, or pathophysiological justification. Therefore, if the clinical question involves interventions, and the evidence found to address the question consists of 2 RCTs, 3 case-control studies, and 3 case series, the evidence would be designated as “level 1 evidence” because study designs with the highest evidentiary level in the available research consisted of RCTs. If all available evidence was from expert opinion, the body of research would comprise “level 4” evidence. This evidence would represent the best available evidence to inform decision-making at the time the assessment was made, although the overall level assigned would change as higher evidentiary level information becomes available.

The levels of evidence approach may be perceived as a quick and easy approach to assessing internal validity because it requires only a knowledge of the study design employed and not the individual features of a study that may or may not be associated with the potential for bias. However, that ease of use is based on very strong assumptions: 1) that study design maps directly to bias, 2) that authors always correctly label study designs, and 3) that authors execute and report study designs appropriately. The approach also pertains to a body of evidence, implying that there are multiple comparable studies available to address the question of interest.

An important critique of levels of evidence is that the approach focuses on the study design, rather than the actual design features that were used or the context of the study. Thus, although this framework illustrates the inherent potential for bias of the different study designs, it does not provide a consideration of the methodological rigor with which any specific individual study was conducted ( 25 ). For instance, although a well-conducted cohort study may be less biased than a poorly executed RCT, this nuance is not captured by a levels of evidence approach. Additionally, levels of evidence are based on the potential for confounding and selection biases, but there is no mechanism to evaluate the potential for information bias because this is linked to the outcome and the levels of evidence approach is based on features at the study, rather than outcome, level. For instance, RCTs provide a higher level of evidence compared to observational studies because random allocation to intervention groups minimizes the potential for confounding, and case-control studies provide a lower level of evidence than cohort studies because they are more prone to selection bias. However, a RCT that used a subjectively measured outcome would be assigned a higher level of evidence than a cohort study with an objective outcome, although the observational study may have a lower risk of information bias. Finally, studies may be mislabeled in terms of their study design; there is empirical evidence that this occurs in the veterinary literature ( 26 – 28 ). For example, studies labeled as case series in veterinary medicine frequently include a component corresponding to a cohort study design ( 27 ); these studies may be assigned an inappropriately low level of evidence if individuals classifying these studies rely on authors terminology rather than the complete design description to determine the design employed.

An additional consideration is that for questions related to aspects of clinical care other than selection of interventions, the framework and positioning of study designs included in Figure 1 may not be appropriate. Levels of evidence schema are available for other clinical questions, such as prognosis, diagnostic test accuracy, disease screening, and etiology ( 29 , 30 ).

Evaluating Internal Validity Based on Inclusion of Study Features Associated With Bias: Quality Assessment

As the name implies, quality assessment represents an evaluation of the quality of a primary research article. However, the term “quality” is difficult to specifically define in the context of evidence-based medicine, in that it does not appear to have been used consistently in the literature. The Merriam-Webster dictionary defines quality as “how good or bad something is” or “a high level of value or excellence” ( https://www.merriam-webster.com/dictionary/quality ). Quality generally is understood to be a multi-dimensional concept. While clear definitions are difficult to find in the research literature, the lay literature includes numerous treaties on the dimensions of quality. One example is the eight dimensions of quality delineated by David Gavin, which include performance, features, reliability, conformance, durability, serviceability, aesthetics, and perceived quality ( https://en.wikipedia.org/wiki/Eight_dimensions_of_quality ).

The findings from a review ( 31 ) identified that available instruments labeled as quality assessment tools varied in clarity and often involved more than just assessing internal validity. In addition to including an assessment of internal validity, quality assessment instruments also generally contain elements related to quality of reporting or an assessment of the inclusion of study features not directly related to bias, such as whether ethical approval was sought or whether the study participants were similar to those animals in the care of the individual doing the critique ( 14 , 31 – 33 ).

Quality assessment as an approach to evaluating internal validity involves an evaluation of the presence or absence of design features, i.e., a methodological checklist ( 14 , 15 ). For example, the Jadad scale ( 17 ) involves completing a checklist of whether the study was described as randomized, whether the study was described as double blind, and whether there was a description of withdrawals and dropouts, with points assigned for each category. Therefore, the Jadad scale uses a quality assessment approach to evaluating internal validity. In terms of assumptions, the quality assessment approach also makes strong assumptions, although these are less than those used in levels of evidence assessments. Instead of mapping bias to the study design, quality assessment maps bias to a design feature i.e., if a trial was randomized, it is assumed to be “good quality” and if the trial was not randomized the assumption is that it is “poor quality”. The same process is followed for additional study aspects, such a blinding or losses to follow-up, and an overall assessment of quality is then based on how the study 'performs' against these questions.

Quality assessment also considers more than just confounding and selection bias as components of internal validity. The inclusion of blinding as a design feature of interest illustrates this. Blinding as a design feature is intended to reduce the potential for differential care as a source of confounding bias (blinding of caregivers) or may be intended to reduce the potential for information bias (blinding of outcome assessors). Conducting a quality assessment is more complicated and time-consuming than evaluating levels of evidence because the presence or absence of the specific design features needs to be identified and validated within the study report. However, the approach requires only that the person evaluating internal validity can identify whether (or not) a design feature was used. Therefore, this approach requires more technical expertise that the levels of evidence approach, but less than the risk of bias approach.

Evaluating Internal Validity by Making Contextualized Judgements on Potential Occurrence of Bias: Risk of Bias Assessment

Risk of bias assessments have been developed specifically for evaluating the potential for elements of the design or conduct employed within a study to lead to a biased effect size ( 34 , 35 ). The components of risk of bias assessments are selected based on empirical evidence of their association with estimates of effect sizes ( 24 , 32 ). The way risk of bias assessments work is that individuals evaluating a study for internal validity answer a series of signaling questions about the presence or absence of design features followed by a judgment about the potential for the use of the design feature to lead to a biased estimate in the context of the specific study. A conclusion is then reached about potential for bias based on all evaluated design features in the context of the study. Thus, a risk of bias assessment makes fewer assumptions about the link between study design and design features compared to quality assessment. For instance, a quality assessment for an RCT would include an evaluation as to whether blinding of outcome assessors occurred, whereas a risk of bias assessment would involve an evaluation not only as to whether blinding was used, but also a judgement as to whether a lack of blinding of outcome assessors would be likely to lead to a biased estimate given the context of the study and the outcome measures used. Thus, a RCT that did not include blinding of outcome assessors might be rated as poor on a quality assessment but might not be a concern in a risk of bias assessment if the outcomes were measured objectively, precluding the likelihood that the estimate would be biased by a knowledge of the intervention group when classifying the outcomes. Because of the necessity of making a judgement about the potential that bias is associated with design features in the context of a specific topic area, this approach requires the highest level of knowledge of study design and bias. The risk of bias approach also generally is conducted at the outcome level, rather than at the study level. For instance, an unblinded RCT of interventions to treat lameness might be considered to have a high risk of bias if the outcome was assessed by owners (a subjective outcome) but not if the outcome was assessed by force plate measurement (an objective outcome). For a level of evidence assessment, the assessment of internal validity would be high quality because the trial was an RCT. For quality assessment, the study may be considered poor quality because it was unblinded, but the overall judgement would be dependent on a number of other study design flaws identified. Finally, in a risk of bias assessment, the study would likely be low risk of bias for the objective outcome and high risk of bias for the subjective outcome if blinding was not used.

Some components of a risk of bias assessment are the same as those included in a quality assessment approach (e.g., an assessment of randomization, allocation concealment, and blinding could be included in both). However, the way the assessment is done differs, with quality assessments generally involving present/absent judgements as opposed to assessments as to whether the risk of bias is likely or not. Hartling et al. ( 14 ) applied two instruments using a quality assessment approach and one instrument using a risk of bias approach to a sample of 163 trials and found that there was low correlation between quality assessment and risk of bias approaches when comparing the assessment of internal validity.

Although the critical elements for risk of bias are well described for RCTs in human healthcare and to a large extent in veterinary RCTs, these elements are not as well described for non-randomized trials and observational studies where allocation to groups is not under the control of the investigator. There are some risk of bias tools available for assessing risk of bias in non-randomized studies, such as ROBINS-I ( 36 ). However, ROBINS-I has been criticized for being challenging to use and for having low reliability, particularly amongst less experienced raters ( 37 , 38 ). A review and critique of approaches to risk of bias assessment for observational studies is available ( 39 ). It is anticipated that risk of bias tools for observational study designs, including studies related to questions of prognosis and causation, will continue to evolve as new instruments are developed and validated.

Historical Contexts and Comparisons of Internal Validity Assessment Approaches

Currently, the available approaches to assessing internal validity tend to be used for different applications. Levels of evidence have previously been used for creating evidence-based recommendations or clinical practices guidelines ( 30 , 40 , 41 ), where it is anticipated that multiple study designs may have been used to address the clinical question(s) of interest. Both quality assessment and risk of bias assessment approaches have been used as a component of systematic reviews with meta-analysis or network meta-analysis, as the intended product of these reviews is to summarize a single parameter (such as incidence or prevalence) or a summary effect size (such as a risk ratio, odds ratio, or hazard ratio) where it is desired that the estimate is unbiased. Often, that estimate is derived from studies with the same study design or a narrow range of study designs from high levels in the evidence hierarchy for the research question type. Therefore, the focus is on a specific parameter estimate based on multiple studies, rather than a descriptive summary of the evidentiary strength of those studies.

However, the different approaches are not necessarily mutually exclusive, but are nested within each other based on assumptions, and the methodology and use of the different approaches has evolved over time. As previously described, a criticism of the use of levels of evidence is that the potential for bias is based on the study design that was employed, rather than the methodological rigor of a specific study ( 42 ). For this reason, many frameworks for levels of evidence included wording such as “appropriately designed” ( 24 ) or “well designed” ( 41 )for the study designs, although the criteria for determining whether a study was designed and executed with rigor generally is not described. A lack of transparency for the criteria for evaluating internal validity of studies within an evidence level is problematic for individuals wishing to use the results. An example of the evolution toward more transparent considerations of internal validity of individual studies within a levels of evidence framework is seen in the progression of the Australian National Health and Medical Research Council (NHMRC) system for evaluating evidence in the development of clinical practice guidelines. The designation of levels of evidence in this framework originally was based on levels of evidence, with descriptors such as “properly-designed” or “well-designed” included for each type of study design ( 40 ). A concern with this approach was that the framework was not designed to address the strength of evidence from individual studies within each evidence level ( 43 ). Therefore, the framework was modified to include the use of risk of bias evaluations of individual studies within each evidence level. The combined use of levels of evidence and risk of bias assessment of studies within each level of evidence now forms the “evidence base” component of the NHMRC's FORM framework for the development of evidence-based clinical guidelines ( 44 ).

Another example of the evolution of approaches to assessing internal validity is from the Cochrane Back review group, who conduct systematic reviews of neck and back pain. The initial methods guidelines, published in 1997, recommended that a quality assessment be performed on each included study, with each item in the quality assessment tool scored based on whether the authors reported their use ( 45 ). Updated methods guidelines were published in 2003 ( 46 ). The framework for levels of evidence in this guidance was restricted to a consideration of randomized controlled trials and non-randomized controlled clinical trials, as these were considered the study designs that potentially were appropriate to address research questions in this content area. In the updated guidelines, the recommendations for the assessment of internal validity moved to a risk of bias approach, where judgements were made on whether the characteristics of each study were likely to lead to biased study results. In the 2003 methods guidelines, levels of evidence were recommended as an approach to qualitative analysis rather than the use of “vote counting” (summing the number of studies where a positive or negative outcome was reported). The guidelines were again updated in 2009 ( 47 ). In this version, the assessment of the internal validity of individual studies explicitly employed a risk of bias approach. It was further recommended that the use of evidence levels as a component of a qualitative synthesis be replaced with a formal rating of the quality of the evidence for each of the included outcomes. It was recommended that review authors use the GRADE approach for this component. The GRADE approach explicitly includes a consideration of the risk of bias across all studies included in the review, as well as an assessment of the consistency of results across studies, the directness of the evidence to the review question, the precision in the effect size estimate, and the potential for publication bias ( 48 ).

The examples from the human medical literature illustrate that assessment of internal validity need not be static, and that modifications to our approach to assessing internal validity can strengthen the evidence base for clinical decision making. When developing or using tools which include an evaluation of internal validity, the assessment of internal validity should use the approach with the least assumptions about bias. This implies that the risk of bias approach, where context specific judgements are made related to the potential for bias, is the preferred approach for assessing internal validity. The risk of bias approach is well developed for RCTs. Therefore, when RCTs are included in the evidence available to address a clinical question, a risk of bias assessment approach should be used. When evaluating internal validity as a component of a SR-MA, the Cochrane ROB2.0 tool ( 16 ) could be used for this purpose. Modifications to this tool have been proposed for evaluating trials in livestock trials ( 49 – 51 ). For critical appraisal instruments for RCTs, where additional components such as feasibility and external validity are a desired component, the questions or items within the instrument that are specific to assessing internal validity still could follow a risk of bias approach by specifically requiring a judgement on the potential for bias. Similarly, the use of questions or items requiring a judgement on the potential for bias also could be used for evaluation of RCTs included in clinical practice guidelines when RCTs are present in the evidence base.

However, there are circumstances where these recommendations may not be appropriate or sufficient, such as for observational studies where risk of bias assessment instruments do not formally exist, or where a variety of study designs have been identified that answer the clinical question (particularly non-intervention type questions). When observational studies are used as evidence, individuals assessing internal validity may wish to evaluate risks of bias for each study ad hoc by considering the specific risks of bias related to selection bias, information bias, and confounding in the context of the topic area. However, this approach requires considerable methodological expertise. Alternatively, a quality assessment approach could be used to evaluate internal validity for observational studies, recognizing that more assumptions related to the potential for bias are involved. As instruments for evaluating the risk of bias for observational studies are developed and validated, these could replace ad hoc or quality assessment approaches.

For situations where the evidence base includes multiple study types, such as clinical practice guidelines, the use of levels of evidence may be useful for framing the potential for bias inherent in the studies identified to address the clinical questions. However, within each evidence level, there still is a need to evaluate the internal validity of each study. The proposed approach for situations where RCTs and observational studies are included in the evidence base was described in the preceding paragraphs. For lower levels of evidence, such as case series, textbooks and narrative reviews, and expert opinion, levels of evidence could be used to emphasize that these types of evidence have high potential for bias based on their design.

Broader Considerations

It should be noted that although this article has focused on approaches to evaluating internal validity of studies, this is only one component of the assessment of evidence. Critical appraisal, CATs, SR-MA, and clinical practice guidelines explicitly incorporate other aspects of decision-making, including a consideration of the magnitude and precision of an intervention effect or the potential clinical impact, the consistency of the research results across studies, the applicability (external validity and feasibility) of the research results, and the directness of the evidence to a clinical situation (for instance, whether the study populations are similar to those in a practice setting). However, a discussion of these components for decision-making is beyond the scope of the current study. The interested reader is referred to further details on the components used in evaluating evidence for CATs ( 4 ), for SR-MA using the GRADE approach ( 52 ), for network meta-analysis ( 53 ) and for clinical practice guidelines ( 8 , 44 ).

Author Contributions

JS drafted the manuscript. All authors contributed equally to the conceptualization of this work. All authors read and approved the final contents.

Partial funding support was obtained from the University of Guelph Research Leadership Chair (Sargeant).

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher's Note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Research on the DCT vehicle starting process evaluation based on LSTM neural network with attention mechanism

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• Zeyu Xu 1 &
• Haijiang Liu 1  

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Currently, with the advancement of dual-clutch transmission (DCT) control systems and vehicle performance, it is necessary to develop better objective evaluation methods for DCT vehicles. The starting process is a critical element affecting the driving and riding experience of DCT vehicles. Therefore, it is crucial to establish and improve a starting process evaluation model for the objective evaluation to DCT vehicles and optimization to DCT control strategies. This paper proposes a new method to evaluate the DCT vehicle starting process objectively. The method analyzes and models the time-series signals of the driving data using the LSTM neural network and uses the attention mechanism to improve the evaluation performance and enhance the interpretability of the evaluation results. Taking the dynamic performance evaluation as an example, the evaluation results indicate that the proposed model is better than the conventional methods, showing notable efficacy and preponderance.

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Acknowledgments

This work was supported by the National Natural Science Foundation of China (No. U1764259).

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Zeyu Xu is currently pursuing the Ph.D. degree in mechanical engineering with Tongji University. His research interests include vehicle evaluation, vehicle detection, data mining and condition identifycation.

Haijiang Liu was born in 1976. He received the B.S., M.S., and Ph.D. degrees in mechanical engineering from Chongqing University. He is currently a Professor and a Doctoral Supervisor with the School of Mechanical Engineering, Tongji University. His research interests include vehicle evaluation, vehicle detection and intelligent manufacturing technology.

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Xu, Z., Liu, H. Research on the DCT vehicle starting process evaluation based on LSTM neural network with attention mechanism. J Mech Sci Technol (2024). https://doi.org/10.1007/s12206-024-0811-8

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Accepted : 14 May 2024

Published : 21 August 2024

DOI : https://doi.org/10.1007/s12206-024-0811-8

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