Hello, I need to analyse an experiment with 3 groups: Control group Treated group 1 (drug 1) Treated group 2 (drug 2) If I use a Kruskal-Wallis test do analyse the data and if I define the control group as the reference group does the test do then the following comparisons? Control group vs. Treated group 1 Control group vs. Treated group 2 Treated group 1 vs. Treated group 2 I am not sure about whether the last comparison is made by the test or not? What happens if I have 4 different groups? Are there then all possible combinations compared? Cheers, Syrvn -- View this message in context: http://r.789695.n4.nabble.com/Question-regarding-Kruskal-Wallis-test-tp4042627p4042627.html Sent from the R help mailing list archive at Nabble.com.