The appraisal step involves critically reviewing a study.
There are variations in the quality of evidence, just like there are variations in the quality of sources found through Google. Some studies are considered to be of a higher quality than others.
Not all results in a resource like PubMed are the same. There are different types of study designs characterized by different types of methodologies.
These studies can be placed in a hierarchy, called the evidence pyramid. The highest quality evidence is located at the top of the pyramid and the lowest quality evidence is located at the bottom.
Systematic Reviews: The Gold Standard
A systematic review is different from the other studies on the pyramid because it is not a study at all, but a literature review.
A group of researchers create a question and search through existing studies for an answer to their question.
Systematic reviews do the legwork for you by searching through the evidence in PubMed and other resources. It is the highest quality evidence because it summarizes multiple studies.
What is a meta-analysis?
A meta-analysis is an optional component of a systematic review. It crunches the numbers of the results in each study and comes up with an aggregate result.
The Evidence Pyramid
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