Function computes sample size for the two-sided Wilcoxon test when applied to two independent samples with ordered categorical responses.
required two-sided Type-I-error level
sample size fraction n/N, where n is sample size of group B and N is the total sample size
number of categories in each group
vector of expected proportions of the categories in group A
vector of expected proportions of the categories in group B
Zhao YD, Rahardja D, Qu Yongming. Sample size calculation for the Wilcoxon-Mann-Whitney test adjsuting for ties. Statistics in Medicine 2008; 27:462-468