A beginner's guide to evidence-based practice in health and social care (4th ed).
How to read a paper: The basics of evidence-based medicine and healthcare (6th ed)
Nursing research: Methods and critical appraisal for evidence-based practice
These selected articles will help you to learn more about critical appraisal.
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Once you have completed the searches you need to answer your question, the next step in the EBP process is to critically appraise the evidence you have found. Critical appraisal is the process of systematically analysing and evaluating the research methodology, data collection methods, and findings of a research study to assess its quality, credibility, and relevance to a specific clinical question (Burls, 2009).
By critically examining the evidence, you will develop an understanding of:
Critically appraising the research evidence is important for a number of reasons, including:
Critically appraising the evidence-base ensures that your practice is underpinned by high-quality evidence, aligns with ethical standards, and aims to positively impact patient care outcomes and service delivery.
Bias refers to any factor that influences the study process or outcomes, resulting in conclusions that may not accurately represent reality. It can develop at various stages of a study, from the way participants are selected to how data is gathered, processed, and reported. Identifying potential bias is crucial when evaluating research in order to establish the study's credibility. There are many types of bias that can impact research studies.
| Type of bias | Definition | Example | How to spot it |
|---|---|---|---|
| Selection bias | Occurs when the study participants are not representative of the target population, leading to skewed results | A study on speech therapy effectiveness that only includes children from high-income families may not reflect outcomes for lower-income families. | Check if study participants were randomly selected and if inclusion/exclusion criteria were clearly defined by the researchers. |
| Performance bias | Happens when study participants or researchers change their behaviour due to knowledge of the study or treatment assignment. | If a therapy study provides additional support beyond the therapy being investigated, to the intervention group, then the results may reflect the additional attention instead of the effectiveness of the therapy. | Check whether the researchers assessing study outcomes were blinded and objective outcome measures were used. |
| Reporting bias | Occurs when only certain results are reported, usually those that support a particular hypothesis or show significant findings. | A pharmaceutical company might publish only the positive results of a new drug trial while not reporting trial results that showed no benefit. | Verify whether all expected outcomes were reported, including negative or non-significant findings. |
| Funding and Conflict of interest bias | Research outcomes can be influenced by who funds the study or the researchers' affiliations. | A study funded by a speech therapy company that concludes its new software is highly effective may be biased if independent studies have not confirmed the results. | Check who funded the study and whether conflicts of interest were disclosed. |
| Attrition bias | Happens when study participants drop out at different rates between the groups, potentially affecting the validity of the findings. | If more participants in the control group drop out of a weight-loss study than those receiving an intervention, it could make the treatment appear more effective than it really is. | Review drop-out rates and see if the researchers accounted for missing data. |
| Racial bias | Occurs when study design, data collection, analysis, or interpretation is influenced by assumptions or systemic inequalities related to race, leading to misrepresentation or exclusion. | A mental health study on university students finds stress as the main cause of depression but only includes White participants. It uses culturally biased screening tools and ignores systemic factors like discrimination. Findings are generalised, risking misdiagnosis and ineffective interventions for diverse populations. | Check if diverse racial/ethnic groups are included and appropriately represented and whether research approaches and tools are appropriate to diverse populations. |
For additional information on the types of bias that can impact research studies, go to Oxford's Catalogue of bias.
In research studies, validity refers to the degree to which a research study accurately measures what it is intended to measure and that the results truly reflect what is being studied. Validity ensures that research findings are accurate, reliable, and applicable to real-world situations.
The impact of a research study assesses its clinical significance and ability to influence real-world practice and decision-making. It considers whether a study's findings have practical applications such as:
Burls, A. (2009). What is critical appraisal? Hayward Medical Communications. https://www.whatisseries.co.uk
