Ridit: Ridit Analysis (An extension of the Kruskal-Wallis Test)

An extension of the Kruskal-Wallis Test that allows selection of arbitrary reference group. Also, provide Mean Ridit for each group. Mean Ridit of a group is an estimate of probability a random observation from that group will be greater than or equal to a random observation from the reference group. This aforementioned method is discussed in "Design and Analysis of Clinical Experiments" by Joseph L. Fleiss.