Re: st: Nemenyi test

[Célia Dechavanne <celia_dv@yahoo.fr>]

Thank you for your help.
My first mail was not enough clear, sorry for that. The five groups are 
small (minimum n=11 and maximum n=26). The KW test gives a significant 
difference between the groups, now I would like to compare 2 by 2. But I 
can't perform pairwise comparison, I would like to compare the shift 
between the five groups. I hope is better clear now.
Thank you so much for the time spent to answer.
Best
Celia

Le mercredi 28 août 18:29, Marta García-Granero a écrit :
> I have Hochberg&Tamhane "Multiple Comparisons Procedures", and there 
> are a couple of references for a Nemenyi procedure, one for pairwise 
> signed ranks tests (after a non-parametric K related samples omnibus 
> test) and another for pairwise median tests, after a k-samples median 
> test (not Kruskal-Wallis). This last method is also known as Levy test.
> Unless there is another "Nemenyi procedure" not mentioned in H&T book, 
> I think Celia is a bit confused, since she has performed a 
> Kruskal-Wallis test, not a k-medians test. Anyway, I have found a web 
> page that described multiple comparisons method named Nemenyi after a 
> KW test...
> Maybe the simplest pairwise comparison method she can use is pairwise 
> rank-sums (AKA: Mann-Whitney's U tests) with Sidak adjustment.
> This program is rather unpolished (absolutely no error trapping or 
> handling), but it does the task (quick&dirty solution):
> program multimw,nclass
> version 12
> args x y
> confirm var `x'
> confirm var `y'
> sum `y',meanonly
> local comp=r(max)*(r(max)-1)/2
> qui levelsof `y',local(levels)
> foreach i of local levels{
>     foreach j of local levels{
>         if `i'<`j'{
>         quietly ranksum `x' if (`y'==`i')|(`y'==`j'), by(`y')
>         display `j'  _c
>         display " vs " `i'  _c
>         display "p = " %6.4f 2*(1-normal(`r(z)')) "    " _c
>         display "p’= " %6.4f 1-(1-2*(1-normal(`r(z)')))^comp
>         }
>     }
> }
> end
>
> It gives both unadjusted and adjusted p-values.
>
> HTH.
> Marta GG
>
> El 27/08/2013 13:22, David Hoaglin escribió:
> > Celia,
> >
> > I'm not sure what you mean by the "Nemenyi test." Kruskal-Wallis and
> > similar tests based on ranks do not compare distributions.  They focus
> > on shifts (e.g., differences in medians among distributions that have
> > the same shape).
> >
> > How do your continuous distributions behave?  What is the reason for
> > comparing the whole distributions?  How large are the samples?
> >
> > David Hoaglin
> >
> > On Tue, Aug 27, 2013 at 2:16 AM, Célia Dechavanne <celia_dv@yahoo.fr> 
> > wrote:
> > > I am attempting to compare the distributions of a continuous variable
> > > between five groups after a Kruskal Wallis in Stata without success.
> > >
> > > I think that Nemenyi test is the one I need, but I don't find 
> > > anything in
> > > Stata. Could you help me to perform this test?
> > >
> > > Thanks for your help,
> > >
> > > --
> > > Célia Dechavanne
> > > INSERM - UMR S665
> > > Equipe 3 - Pathogénèse du paludisme sévère
> > > 6, rue Alexandre Cabanel
> > > 75739 Paris Cedex 15
> > >
> > >
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