eng Science and Education Publishing American Journal of Applied Mathematics and Statistics 2328-7292 2013-10-22 1 1 99 102 10.12691/ajams-1-5-4 AJAMS2013154 article Norman N. Haidous ac6702@wayne.edu 1 Shlomo S. Sawilowsky 1 Department of Evaluation and Research, Wayne State University, Detroit, USA The purpose of the study was to compare the power and accuracy of the Kornbrot rank difference test to classical parametric and nonparametric alternatives when the assumption of normality is not met, the data are ordinal, and the sample size is small. Although the procedure is robust, there was no evidence the rank difference test had power advantages over Wilcoxon Signed-Ranks test. http://pubs.sciepub.com/ajams/1/5/4/ajams-1-5-4.pdf nonparametric statistics power rank tests Monte Carlo simulations