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...other to report. (The biggest or the smallest). Why is only one being reported? Also I have two implementations of the algorithm. One at http://en.wikipedia.org/wiki/Mann-Whitney_U_test calculates U then generates a normal random variable as (U-Mu)/S and one from http://faculty.vassar.edu/lowry/webtext.html that does not use U instead uses the ranks directly. The second algorithm agrees with the output of wilcox.test in R. Why calculate U, or W, at all? cheers Worik [[alternative HTML version deleted]]

Dear All, I have a problem understanding the difference between the outcome of a fisher exact test and a chi-square test (with simulated p.value). For some sample data (see below), fisher reports p=.02337. The normal chi-square test complains about "approximation may be incorrect", because there is a column with cells with very small values. I therefore tried the chi-square with