randomized control trial, RCT, randomized trial, randomized controlled trial (should not be used)
Randomized studies, commonly called randomized trials, are a treatment comparison in which two or more treatments, possibly including a placebo or withholding a treatment, are compared after random allocation of participants to treatment comparison groups.
Random allocation ensures that each participant has a known (usually an equal) chance of being assigned to any given group. This results in treatment comparison groups that are similar in terms of prognostic variables, whether or not these have been recognised.
Thus, there is generally a lower risk of allocation bias in randomized studies than there is in non-randomized studies.
We advise against using the term "randomized controlled trial" because of ambiguity about what the adjective "controlled" adds.
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