In the Evidence-Based Practice process, and especially in the process of evaluating primary research, we need to critically appraise certain aspects of the evidence we have located. Even when we have found a study that is the right sort of study for our clinical question, and is of the appropriate level in the hierarchy, we still need to question its relevance, validity, and conclusions. The three main questions to be asked are:

• Is the study relevant to our clinical question?
• How well was the study done?
• What do the results mean and are they statistically valid (and not just due to chance)?

• The Critical Appraisal Skills Programme (CASP) is part of Better Value Healthcare, a training organisation led by Professor Sir Muir Gray, and based in Oxford. It is best known for its checklists, a set of eight critical appraisal tools designed to be used when reading research.