Critical appraisal is the process of carefully and systematically examining research to judge its trustworthiness, and its value and relevance in a particular context (Burls, 2009). Critical appraisal of studies involves checking the quality, reliability and relevance of the studies you've selected to help answer your review question. Depending on the type of study you are evaluating you may use different evaluation tools. When evaluating studies, some questions to consider are:

• ​​​​Has the study's aim been clearly stated?
• Does the sample accurately reflect the population?
• Has the sampling method and size been described and justified?
• Have exclusions been stated?
• Is the control group easily identified?
• Is the loss to follow-up detailed?
• Can the results be replicated?
• Are there confounding factors?
• Are the conclusions logical?
• Can the results be extrapolated to other populations?