Randomized concurrently controlled clinical trial;  Randomized controlled clinical trial

A randomized clinical trial is one in which the subjects in each treatment group have been placed in that group by a randomization procedure. Randomization involves randomly assigning experimental subjects to one of the treatment groups so that many potential influences that cannot be controlled for (e.g., height, weight) or cannot be determined by observation (e.g., specific metabolic pathway influences that may be relevant to the efficacy or safety of interventions in the trial) are likely to be as frequent in one treatment group as they are in the other (Turner, 2010).

The fundamental goal of randomization is to eliminate bias (or, pragmatically, to reduce it as much as possible). This includes subject bias, based on their knowledge of which treatment/intervention group they have been assigned to, and investigator bias. Investigator bias is eliminated by...