Peter Dalgaard wrote: > Bob Green <[EMAIL PROTECTED]> writes: > > >>An earlier post had posed the question: "Does anybody know what is relation >>between 'T' value calculated by 'wilcox_test' function (coin package) and >>more common 'W' value?" >> >>I found the question interesting and ran the commands in R and SPSS. The W >>reported by R did not seem to correspond to either Mann-Whitney U, >>Wilcoxon W or the Z which I have more commonly used. Correction for ties >>may have affected my results. >> >>Can anyone else explain what the reported W is and the relation to the >>reported T? > > > Well, it's open source... You could just go check. > > W is the sum of the ranks in the first group, minus the minimum value > it can attain, namely sum(1:n1) == n1*(n1+1)/2. In the tied cases, the > actual minimum could be larger. > > The T would seem to be asymptotically normal > > >>wilcox_test(pd ~ age, data = water_transfer,distribution="asymp") > > > Asymptotic Wilcoxon Mann-Whitney Rank Sum Test > > data: pd by groups 12-26 Weeks, At term > T = -1.2247, p-value = 0.2207 > alternative hypothesis: true mu is not equal to 0 > > >>pnorm(-1.2247)*2 > > [1] 0.2206883 > > so a good guess at its definition is that it is obtained from W or one > of the others by subtracting the mean and dividing with the SD. >
With the SD adjusted for ties, of course. (See, e.g., Conover's book.) Peter Ehlers University of Calgary ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html