ABSTRACT
Response-adaptive randomization or allocation is a randomization tech-
nique in which the allocation of patients to treatment groups is based on
the responses (outcomes) of the previous patients. The main purpose is to
provide a better chance of randomizing the patients to a superior treatment
group based on the knowledge about the treatment effect at the time of
randomization. As a result, response-adaptive randomization takes ethical
concerns into consideration. The well-known response-adaptive models in-
clude the play-the-winner (PW) model and the randomized play-the-winner
(RPW) model.