title: Randomization in controlled clinical trials: why the flip of a coin is so important.
abstract: The randomized controlled trial (RCT) is considered the highest level of medical evidence. In this brief overview, we discuss several key principles of the RCT. First, balance is paramount. Comparison groups must have similar proportions of participants with "important" prognostic and confounding factors. Randomization may or may not achieve this balance; if it does not, statistical adjustments should be used. Second, a statistical analysis should emphasize comparability and not mask dissimilarity. If the trial was indeed randomized, certain analysis techniques, such as an intention to treat analysis, should always be presented. Third, additional bias-reducing techniques, such as concealing treatment assignments from treating physicians and participants (i.e., masking) and using clearly defined exclusion and inclusion criteria, should be used wherever possible.
authors.affiliation: From the Center for Statistical Sciences, Brown University, Division of Research, Rhode Island, USA.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Blume
authors.forename: Jeffrey F
authors.initials: JF
authors.lastname: Peipert
mesh_terms: D006801:Humans; D017063:Outcome Assessment, Health Care; D018579:Patient Selection; D011897:Random Allocation; D016032:Randomized Controlled Trials as Topic / Q000379:methods / Q000592:standards