Wilcoxon Matched-Pairs Signed-Ranks Test

Abstract

The Wilcoxon Matched-Pairs Signed Ranks Test is a nonparametric test that is often viewed as being similar to Student’s t-Test for Matched Pairs, but it is used for ordinal data or data that seriously violate any semblance of normal distribution. Of course, there are many who would argue that it is simply too convenient to compare the Wilcoxon Matched-Pairs Signed Ranks Test to Student’s t-Test for Matched Pairs even though they serve similar purposes. Group differences for when there are two matched pairs are addressed by both tests, but again, the Wilcoxon Matched-Pairs Signed Ranks Test is often used with ordinal data and/or data that are viewed as being nonparametric (with attention to medians) whereas the Student’s t-Test for Matched Pairs is generally used with interval data that rise to the level of parametric distributions (with attention to means). This lesson is interesting in that there is a tied set of values for one of the matched pairs, which introduces some degree of complexity on how values are ranked when there are ties (i.e., for an individual matched pair, there is no difference in the two scores that are being compared).