This requires a basic knowledge of the types of information resources, an understanding of the levels of evidence, knowledge of basic study design, and the questions that need to be asked to evaluate the scientific quality of an individual research study.
If you were able to find information that answered your formulated question using any of the Summaries of the Evidence or Critically Appraised Research sites in Step 2, you can be assured that you have found valid information and can move onto Step 4.
However, if you also searched a database such as CINAHL or PubMed, the research articles you retrieved must be evaluated for scientific quality. Critically appraising the quality of a scientific study is a complex process, but there are many tools to assist you in the process. To begin, a few basic questions may help you determine if a study is reliable and provides valid information.