Blinding refers to the concealment of group allocation from one
or more individuals involved in a clinical research study, most
commonly a randomized controlled trial (RCT)
Randomization minimizes differences between treatment groups at
the outset of the trial, it does nothing to prevent differential
treatment of the groups later in the trial or the differential
assessment of outcomes, either of which may result in biased
estimates of treatment effects.
The optimal strategy to minimize the likelihood of differential
treatment or assessments of outcomes is to blind as many
individuals as possible in a trial.