Re: [R] Two factor (or more) non-parametric comparison of means

From: Peter Dalgaard <p.dalgaard_at_biostat.ku.dk>
Date: Wed 12 Oct 2005 - 03:46:52 EST

"Marc Schwartz (via MN)" <mschwartz@mn.rr.com> writes:

> I suspect that John may be looking for ?friedman.test, which I believe
> will allow for a two-way non-parametric test.

You could be right, but you could also be wrong... It depends quite a bit on what is meant by a "two-factor comparison of means". If he literally means means (!), then a permutation test (permuting within levels of the other factor) could be appropriate. It also makes a difference whether there's a single replication or more per cell in the cross-classification.

> kruskal.test() will perform a non-parametric test on two or more samples
> (or factor levels) as a generalization of wilcox.test() for one or two
> samples (or factor levels).
>
> HTH,
>
> Marc Schwartz
>
> On Tue, 2005-10-11 at 18:22 +0200, Johan Sandblom wrote:
> > ?kruskal.test
> >
> > 2005/10/11, John Sorkin <jsorkin@grecc.umaryland.edu>:
> > > Can anyone suggest a good non-parametric test, and an R
> > implementation of the test, that allows for two or more factors?
> > Wilcoxon signed rank allows for only one.
> > > Thanks,
> > > John
>
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-- 
   O__  ---- Peter Dalgaard             ุster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)                  FAX: (+45) 35327907

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Received on Wed Oct 12 03:49:29 2005

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