Abstract: Urn model is a most commonly used randomization method of adaptive design. In this article, given the study time were from 6 to 12 months and the interview time were from 7 to 56 days, urn model was used to calculate the allocation proportions between the two treatments groups through simulation experiments. The outcomes indicated that the effects of study duration and interview duration on randomization results exactly exist, but they were not as serious as we assumed for the differences of effective modulus were not significant. We hope this study can provide some references for the application of RPW rule in practical clinical trials.

Key words: Adaptive design, Urn model, Simulation examination, RPW rule