The objective of clinical trials is to establish the effect of an intervention. Treatment effects
are efficiently isolated by controlling for bias and confounding and by minimizing variation.
Key features of clinical trials that are used to meet this objective are randomization (possibly
with stratification), adherence to intent-to-treat (ITT) principles, blinding, prospective
evaluation, and use of a control group. Compared to other types of study designs (e.g., casecontrol studies, cohort studies, case reports), randomized trials have high validity but are
more difficult and expensive to conduct.