[R] BIZARRE results from wilcox.test()

Daniel Malter daniel at umd.edu
Wed Jun 15 20:12:51 CEST 2011


I did not intend to bully you but rather tried to speak narrowly to the core
of the issue. In a sense the point was that the example you used to
illustrate the problem created part of the problem and that in a sensical
dataset you would not obtain nonsensical results. Secondly, my reply talked
to the solution of your problem by pointing out that the test uses the
normal approximation by standard, which is exactly that: an approximation,
implying that avoiding the approximation may solve the issue. This is what
exact=T does, as you figured out.

Daniel




genecleaner wrote:
> 
> Dear Daniel and Sarah, 
> 
> Thanks you for your rude replies .
> The script that I provided was only an example and to illustrate the
> problem. It makes perfectly sense to use the Wilcoxon test on my datasets.
> However, you replies were nonsensical, since you could not solve the
> problem but rather just bullied me.
> 
> Anyway, this is the solution to the problem: the exact=TRUE statement
> should be added
> 
>> w <- wilcox.test(c(1:50),(c(1:50)+100))
>> w$p.value
> [1] 7.066072e-18
>> w <- wilcox.test(c(1:50),(c(1:50)+100), exact=TRUE)
>> w$p.value
> [1] 1.982331e-29
> 
> Best regards,
> genecleaner
> 

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