An Omnibus Consistent Adaptive Percentile Modified Wilcoxon Rank Sum Test with Applications in Gene Expression Studies
Thas, Olivier × Clement, Lieven Rayner, John C. W. Carvalho, B. Van Criekinge, Wim #
Biometrics vol:68 issue:2 pages:446-454
We present an adaptive percentile modiﬁed Wilcoxon rank sum test for the two-sample problem. The test is basically a Wilcoxon rank sum test applied on only a fraction of the sample observations, and the fraction is adaptively determined by the sample observations. Most of the theory is developed under a location-shift model, but we demonstrate that the test is also meaningful for testing against more general alternatives. The test may be particularly useful for the analysis of massive datasets in which quasi-automatic hypothesis testing is required. We investigate the power characteristics of the new test in a simulation study, and we apply the test to a microarray experiment on colorectal cancer for which a differentially expressed gene is detected that could not be detected by the t and the Wilcoxon rank sum tests. This ﬁnding has been conﬁrmed in a biological validation experiment.