Allocation concealment
In a randomized experiment, allocation concealment hides the sorting of trial participants into treatment groups so that this knowledge cannot be exploited.The authors justified the introduction of the term: “The reduction of bias in trials depends crucially upon preventing foreknowledge of treatment assignment.Concealing assignments until the point of allocation prevents foreknowledge, but that process has sometimes been confusingly referred to as 'randomization blinding'.First, the rationale for generating comparison groups at random, including the steps taken to conceal the assignment schedule, is to eliminate selection bias.By contrast, other forms of blinding, used after the assignment of treatments, serve primarily to reduce ascertainment bias.