Re: [R] Wilcoxon signed rank test and its requirements

From: Joris Meys <>
Date: Wed, 23 Jun 2010 23:51:19 +0200

On Wed, Jun 23, 2010 at 10:27 PM, Atte Tenkanen <> wrote:
> Hi all,
> I have a distribution, and take a sample of it. Then I compare that sample with the mean of the population like here in "Wilcoxon signed rank test with continuity correction":
>> wilcox.test(Sample,mu=mean(All), alt="two.sided")
>        Wilcoxon signed rank test with continuity correction
> data:  AlphaNoteOnsetDists
> V = 63855, p-value = 0.0002093
> alternative hypothesis: true location is not equal to 0.4115136
>> wilcox.test(Sample,mu=mean(All), alt = "greater")
>        Wilcoxon signed rank test with continuity correction
> data:  AlphaNoteOnsetDists
> V = 63855, p-value = 0.0001047
> alternative hypothesis: true location is greater than 0.4115136
> What assumptions are needed for the population?

wikipedia says:
"The Wilcoxon signed-rank test is a _non-parametric_ statistical hypothesis test for... "
it also talks about the assumptions.

> What can we say according these results?
> p-value for the "less" is 0.999.

That the p-value for less and greater seem to sum up to one, and that the p-value of greater is half of that for two-sided. You shouldn't ask what we can say. You should ask yourself "What was the question and is this test giving me an answer on that question?"


Joris Meys
Statistical consultant

Ghent University
Faculty of Bioscience Engineering
Department of Applied mathematics, biometrics and process control

tel : +32 9 264 59 87
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Received on Wed 23 Jun 2010 - 21:54:04 GMT

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