Wilcoxon Signed-Rank Test

Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The Wilcoxon signed-rank test is a non-parametric statistical hypothesis test for the case of two related samples or repeated measurements on a single sample. It can be used as an alternative to the paired Student's t-test when the population cannot be assumed to be normally distributed. The test is named for Frank Wilcoxon (18921965) who, in a single paper, proposed both it and the rank-sum test for two independent samples (Wilcoxon, 1945). Like the paired or related sample t-test, the Wilcoxon test involves comparisons of differences between measurements, so it requires that the data are measured at an interval level of measurement. However it does not require assumptions about the form of the distribution of the measurements. It should therefore be used whenever the distributional assumptions that underlie the t-test cannot be satisfied.