[R] Wilcoxon Mann-Whitney Rank Sum Test

From: Tuszynski, Jaroslaw W. <JAROSLAW.W.TUSZYNSKI_at_saic.com>
Date: Sat 17 Dec 2005 - 03:52:55 EST


Does anybody know what is relation between 'T' value calculated by 'wilcox_test' function (coin package) and more common 'W' value?

Jarek Tuszynski

>library(coin)
> ### Tritiated Water Diffusion Across Human Chorioamnion
> ### Hollander & Wolfe (1999), Table 4.1, page 110
> water_transfer <- data.frame(

+     pd = c(0.80, 0.83, 1.89, 1.04, 1.45, 1.38, 1.91, 1.64, 0.73, 1.46,
+            1.15, 0.88, 0.90, 0.74, 1.21),
+     age = factor(c(rep("At term", 10), rep("12-26 Weeks", 5))))

>
> ### Wilcoxon-Mann-Whitney test, cf. Hollander & Wolfe (1999), page 111
> ### exact p-value and confidence interval for the difference in location
> ### (At term - 12-26 Weeks)
> wt <- wilcox_test(pd ~ age, data = water_transfer, distribution = "exact",

conf.int = TRUE)
> print(wt)

        Exact Wilcoxon Mann-Whitney Rank Sum Test

data: pd by groups 12-26 Weeks, At term T = -1.2247, p-value = 0.2544
alternative hypothesis: true mu is not equal to 0 95 percent confidence interval:
 -0.76 0.15
sample estimates:
difference in location

                -0.305 

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