Different types of research present different kinds of evidence. Think of evidence as being arranged in a hierarchy or pyramid. Studies at the top of the evidence pyramid have a higher value but fewer are created.
The following table tells you what types of evidence you should look for depending on the question type you are researching. For each question type, the most reliable evidence is listed first, followed by less reliable evidence.
|Therapy (Treatment)||randomized control trial|
|Prevention||randomized control trial >> cohort study|
|Diagnosis||prospective, blind comparison to a gold standard|
|Prognosis (Forecast)||cohort study >> case control study >> case series study|
|Etiology/Harm (Cause)||randomized control trial >> cohort study >> case control study >> case series study|