Critical appraisal is the process of assessing the quality of a piece of research. This is an essential step in determining whether or not to use the research in your own work. In order to make an informed decision, you need to be able to evaluate the study’s strengths and weaknesses. We will discuss how to critically appraise a research study, and cover the five main criteria of critical appraisal: validity, reliability, bias, precision, and accuracy.
What is critical appraisal and why is it important
Critical appraisal is the process of assessing the quality of a piece of research. It is important to critically appraise a study before using its findings because otherwise you might base your work on faulty information. By taking the time to assess a study’s strengths and weaknesses, you can determine whether or not it is suitable for your purposes
The steps of critical appraisal
When critically appraising a study, there are a few key questions you should keep in mind:
- Is the study valid?
- Is the study reliable?
- Is there any bias in the study?
- Is the study precise?
- Is the study accurate?
We will discuss each of these questions in more detail below.
- What is validity? Validity refers to how well a study measures what it sets out to measure. A valid study is one that produces results that are accurate and representative of the population or phenomenon being studied. There are two main types of validity, internal and external validity. It is crucial for a study to be valid because if it is not, its findings cannot be trusted.
- What is reliability? Reliability refers to how consistent a study’s results are. A reliable study is one that would produce the same results if it were conducted again. There are two main types of reliability: internal and external. Internal reliability refers to the consistency of results within a study, while external reliability refers to the consistency of results across studies.
- What is bias? Bias occurs when a researcher allows their personal beliefs or prejudices to influence the results of a study. Bias can be either intentional or unintentional. There are four main types of bias: selection, information, measurement, and analysis.
- What is precision? Precision refers to how specific a study’s results are. A precise study is one that provides detailed and specific information about the population or phenomenon being studied.
- What is accuracy? Accuracy refers to how close a study’s results are to the true value. An accurate study is one that provides results that are close to the actual value.
How to critically appraise a study
The first step in critically appraising a study is to identify its strengths and weaknesses. You can do this by using the CASP (Critical Appraisal Skills Programme) checklist.
The CASP checklist consists of eight questions:
- What are the research question(s)?
- What are the study design and methods?
- Was the assignment of participants to treatment groups randomized?
- Were all participants who entered the trial properly accounted for at its conclusion?
- Were those not receiving the experimental treatment treated similarly to those receiving it?
- How were patients, staff, and investigators kept unaware of which patients were assigned to which treatment group until after interventions had been allocated?
- Outcome measures adequately sensitive to detect clinically important effects?
- Were the results of the primary and secondary outcome measures similar?
Applying critical appraisal to your own research
When conducting your own research, it is important to critically appraise the studies you are using. This will help you determine whether or not the findings are trustworthy. The CASP (Critical Appraisal Skills Programme) template is a valuable tool for identifying the strengths and weaknesses of a study.
For example, let’s say you are conducting a study on the effects of metformin on cognitive performance. You find a study that looks at this topic and decide to use it in your own research. However, upon closer inspection, you realize that the study has several methodological flaws. For example, the participants were not randomly assigned to either the metformin (intervention arm) or control group.
Because of this, you would conclude that the findings of the study are not trustworthy and decide not to use it in your own research. This is an example of how critical appraisal can help you make informed decisions about which studies to use in your own work. By taking the time to critically appraise a study, you can ensure that you are using accurate and precise research in your own work.
Resources for further learning
The Critical Appraisal Skills Programme (CASP) website provides a range of resources to help you learn how to critically appraise research. They offer a self-directed learning course, as well as a selection of tools and checklists that can be used to appraise research studies.
The Cochrane Collaboration also offers resources on critical appraisal. Their website includes an overview of critical appraisal, as well as a number of articles and podcasts on the topic.
A concise critical appraisal course.
Glossary of key terms
- CASP: Critical Appraisal Skills Programme – an international organisation that offers resources to help people learn how to critically appraise research.
- Critical appraisal: The process of assessing the quality of a research study. This includes looking at the study design, methods, and results, in order to determine whether or not the findings are trustworthy.
- Study design: The way in which a study is conducted. This includes the type of study (e.g., randomized controlled trial), as well as the specific methods used (e.g., questionnaires, interviews).
- Methods: The specific procedures used to conduct a study. This can include things like data collection methods (e.g., surveys) and analysis methods (e.g., statistical tests).
- Results: The findings of a study. This can include both the quantitative data (e.g., means and standard deviations) and the qualitative data (e.g., themes and quotes).
- Trustworthy: A term used to describe research that is of high quality and accurate. Studies that are trustworthy can be relied upon to provide accurate information about a topic.
- Accurate: A term used to describe research that provides correct information about a topic. Studies that are accurate provide information that is free from error or bias.
- Precise: A term used to describe research that provides specific information about a topic. Studies that are precise provide detailed and specific information about a topic.
- Bias: A term used to describe when a study is not conducted in a neutral or objective manner. Bias can occur when the researcher has a personal stake in the outcome of the study, or when the study is designed in such a way that it is likely to produce desired results.
References
- Purssell E. Can the Critical Appraisal Skills Programme check-lists be used alongside Grading of Recommendations Assessment, Development and Evaluation to improve transparency and decision-making? J Adv Nurs. 2020 Apr;76(4):1082-1089.
- Cipriani A, Furukawa TA, Barbui C. What is a Cochrane review? Epidemiol Psychiatr Sci. 2011 Sep;20(3):231-3.
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