Statistics in medicine
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Statistics in medicine · Feb 2008
Sample size calculation for the Wilcoxon-Mann-Whitney test adjusting for ties.
In this paper we study sample size calculation methods for the asymptotic Wilcoxon-Mann-Whitney test for data with or without ties. The existing methods are applicable either to data with ties or to data without ties but not to both cases. ⋯ In addition, the new method can be applied to both data with or without ties. Simulations have demonstrated that the new sample size formula performs very well as the corresponding actual powers are close to the nominal powers.