Critical appraisal skills focus on expecting the conclusions reached by research reports to be justified by the data collected. The type of evidence (for example, qualitative or quantitative) and the ways or methods by which it was gathered (for example, a survey, a randomised trial, or a focus group) will have an impact on how confident you are about the conclusions it puts forward. The evidence from some methods, such as larger studies and systematic reviews, tends to be seen as more reliable than that from others. However, all methods, from a large systematic review of a number of random controlled trials to a single case study, have their own merits and are appropriate at different times.
The following resources give a brief overview of different research methods and also cover general points for appraising research and more specific issues relating to particular types of research methods.