[R] Mann Whitney test
Frank E Harrell Jr
f.harrell at vanderbilt.edu
Sat Feb 14 15:50:34 CET 2009
Daniel Moreira wrote:
> Wilcoxon?Mann?Whitney allows arbitrary sample sizes. It is an extension of
> the original Wilcoxon test which only handles equal sample sizes.
> Daniel Moreira, MD
I believe you'll find that the Wilcoxon 2-sample test always allowed for
unequal sample sizes. To be clear there is the Wilcoxon 2-sample test
(Wilcoxon-Mann-Whitney 2-sample rank-sum test, to be precise) and the
Wilcoxon signed-rank one sample test, usually used for paired data (in
which the sample sizes are equal by definition since with paired data we
subtract a f(pre) from f(post) where f is a suitable transformation for
the pre and post measurements from the same subject).
> Research Associate
> Duke University Medical Center
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> Rodrigo Fernandes Ramalho <rofera at ig.com.br>
> Sent by: r-help-bounces at r-project.org
> 02/14/2009 08:52 AM
> r-help at r-project.org
> [R] Mann Whitney test
> I have a statistical question.
> To apply the Mann Whitney test to compare a pair of vectors, they must to
> have the same length ?
> [[alternative HTML version deleted]]
> R-help at r-project.org mailing list
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> and provide commented, minimal, self-contained, reproducible code.
Frank E Harrell Jr Professor and Chair School of Medicine
Department of Biostatistics Vanderbilt University
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