[R] How to calculate the power of Wilcoxon signed rank test

Tianchan Niu Niu at isis.georgetown.edu
Tue Sep 13 22:51:36 CEST 2011

Thank you David for your reply. But I am still confusing.

I am using Wilcoxon test to compare two samples to assess whether their means differ because neither of them is normally distributed.
Is it possible to compute the power of the Wilcoxon test similar to that of t test? Or is it just a wrong question?

Thank you!
From: David Winsemius [dwinsemius at comcast.net]
Sent: Tuesday, September 13, 2011 4:24 PM
To: Tianchan Niu
Cc: r-help at r-project.org
Subject: Re: [R] How to calculate the power of Wilcoxon signed rank test

On Sep 13, 2011, at 3:34 PM, tn85 wrote:

> Hello All,
> I perform a Wilcoxon signed rank test for two sets of data to test
> whether
> they two have significantly different means. I would also like to
> know the
> power of this test.

Given that none of the various "Wilcoxon tests" are for differences in
means, you are proposing it for the wrong purpose.

> The third part of this tutorial is similar to what I want except the t
> distribution.  http://www.cyclismo.org/tutorial/R/power.html#multiT
> Could anyone help? Or let me know if my question is a nonsense one.
> Thanks
> in advance.


David Winsemius, MD
West Hartford, CT

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