A clinical trial may be defined as a ‘‘planned exper- iment’’ that involves patients, and it is designed to elucidate the most appropriate treatment of future patients with a given medical condition. The first step in designing a clinical trial is to select the best study type. The major types are the case report, the case series, case control studies, cohort study, and the most rigorous of all study designs; the randomized controlled trial (RCT). The basic design features of an RCT are randomization including stratification, permuted blocks, timing and blinding, measurement of outcome, sample size, analysis, and feasibility.