Claus Atzenbeck <[EMAIL PROTECTED]> writes: > On Tue, 15 Nov 2005, Peter Dalgaard wrote: > > > > > However, for Wilcoxon tests, the formula for effect sizes is: > > > > r = Z / sqrt(N) > > > > > > > > I wonder how I can calculate the Z-score in R for a Wilcoxon test. > > > > > > Does anyone know how to calculate effect sizes for Wilcoxon tests as > > > SPSS can do? I wonder if it would be very difficult to do so with R. > > > > If the above formula is correct, it can't be hard. What I wonder is > > whether (and if so, how) it makes sense. (& the fact that SPSS does it > > is no guarantee...) > > According to my references, the formula is OK. > > However, how do I get Z from a Wilcoxon test in R?
Well it's the quantity that is fed to pnorm in the calculation of the approximate p-value, so how about inverting it using e.g. qnorm(wilcox.test(....., exact=FALSE, alternative="less")$p.value) if you don't want to pick stats:::wilcox.test.default apart. You might also throw in correct=FALSE, but I see no objective argument for doing so or not. > (BTW, I have to correct myself: SPSS delivers Z. The effect size was > calculated by the author of one of my books using the above mentioned > formula.) > > Claus > -- O__ ---- Peter Dalgaard Øster Farimagsgade 5, Entr.B c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907 ______________________________________________ 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
