By identifying the type of clinical question you can determine the study design that will provide the best evidence to address that question. The question type and study design can be incorporated into your database search strategy.
Therapy/Treatment: Randomized controlled trial
Diagnosis: Prospective, blind comparison to gold standard
Prognosis: Cohort study > case control > case series
Etiology/Harm: Randomized controlled trial > cohort study > case control > case series
