7. Adaptive Randomization

  1. Guosheng Yin

Published Online: 9 JAN 2012

DOI: 10.1002/9781118183335.ch7

Clinical Trial Design: Bayesian and Frequentist Adaptive Methods

Clinical Trial Design: Bayesian and Frequentist Adaptive Methods

How to Cite

Yin, G. (2011) Adaptive Randomization, in Clinical Trial Design: Bayesian and Frequentist Adaptive Methods, John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9781118183335.ch7

Publication History

  1. Published Online: 9 JAN 2012
  2. Published Print: 19 DEC 2011

ISBN Information

Print ISBN: 9780470581711

Online ISBN: 9781118183335



  • adaptive randomization;
  • biased coin design (BCD);
  • drop-the-loser rule;
  • fixed randomization (FR);
  • permuted block randomization;
  • play-the-winner rule;
  • stratified randomization


In general, randomization can be classified as follows: simple randomization; permuted block randomization; stratified randomization; and adaptive randomization (AR). In a two-arm randomized study, the biased coin design (BCD) can be used to sequentially allocate patients between the two treatments. The play-the-winner rule is a simple response-adaptive design. Similar to the play-the-winner rule, the drop-the-loser rule also assigns more patients to a better treatment. The drop-the-loser rule may produce a less variable proportion during patients' allocation to treatment groups. The doubly adaptive biased coin design allows the randomization probability to explicitly depend on both the observed allocation proportion and the estimated target allocation ratio. Although various AR procedures are available, the conventional fixed randomization (FR) remains its dominant role in clinical trials.

Controlled Vocabulary Terms

permutation test; randomization