search for: wilcox_exact

...even, with ties. I have the following scenario: #---BeginCode--- # big example size = 60 big1 = rnorm(size, 0, 1) big2 = rnorm(size, 0.5, 1 g1f = rep(1, size) g2f = rep(2, size) big = c(big1, big2) data_frame = data.frame(big, gr=as.factor(c(g1f, g2f))) wilcox_approx = wilcox.test(big1, big2) wilcox_exact = wilcox_test(big ~ gr, data=data_frame, distribution="exact") #---EndCode--- I found here http://www-stat.stanford.edu/~susan/courses/s141/hononpara.pdf that wilcox.test (at least for the signed rank test) relies on exact (p-)values until N = n1 + n2 = 50. I can reproduce this, when u...

...d in their p-values (0.167 resp. 0.172). It turns out that SPSS rounds off an entry which is equal to -0.899999999999999 to -0.9 (thus producing a tie at this position). While the former entry probably is the result of some stupid algorithmic twist in some software (take your guesses), I think that wilcox_exact in the coin package is superior by not assuming that data are to be tied when deemed close enough by some poor defined measure (but I'm biased). Try wilcox_test(delta_hba1c~as.factor(Treatment), data=U, distribution="exact") And wilcox_test(signif(delta_hba1c,3)~as.factor(Treatment)...