Quick and simple approximation of sample sizes for comparing two independent binomial distributions: different-sample-size case.

Given the ratio, k, of two sample sizes, sample sizes for comparing two independent proportions can be approximated from the sample size for the equal-sample-size design. The proposed method is compared to the method of Fleiss , Tytun and Ury (1980, Biometrics 36, 343-346). Methods for choosing the ratio are also presented.