On Jan 12, 2012, at 14:11 , Frank Harrell wrote: > The Kruskal-Wallis test is a special case of the proportional odds ordinal > logistic model.
Eh? Can you elaborate on that? I would expect that at best it is equivalent to some _test_ in a polr-type model. It is never really clear what the model is when some groups are different and others not. > You can get any contrast you want by testing regression > coefficients. In a couple of weeks the rms package's contrast function > will allow for individual confidence intervals of effects that together have > a 0.05 type I error, by using the multcomp package (called automatically > from contrast.rms). > Frank > > Iasonas Lamprianou wrote >> >> Thank you for the result, I will have a look at the link. >> >> >> Dr. Iasonas Lamprianou >> Department of Social and Political Sciences >> University of Cyprus >> >> >>> ________________________________ >>> From: Tal Galili <tal.galili@> >>> To: Iasonas Lamprianou <lamprianou@> >>> Cc: "r-help@" <r-help@> >>> Sent: Thursday, 12 January 2012, 10:48 >>> Subject: Re: [R] kruskal wallis post hoc? >>> >>> >>> Hi Iasonas , >>> This is a stat question and not an R question. >>> But the general answer is that it could happen :) >>> >>> >>> The R question would have been if their is a Tukey HSD for kruskel.test, > the answer is yes: >>> http://stats.stackexchange.com/questions/17342/is-there-a-nonparametric-equivalent-of-tukey-hsd >>> >>> But if you didn't get any significant result from the pairwise comparison, > I would say that the post hoc correction wouldn't help you (it could be that > the reason for this significance is based on some weird contrast...) >>> >>> >>> Best, >>> Tal >>> >>> >>> >>> >>> >>> >>> >>> >>> ----------------Contact > Details:------------------------------------------------------- >>> Contact me: Tal.Galili@ | 972-52-7275845 >>> Read me: www.talgalili.com (Hebrew) | www.biostatistics.co.il (Hebrew) | > www.r-statistics.com (English) >>> ---------------------------------------------------------------------------------------------- >>> >>> >>> >>> >>> >>> On Thu, Jan 12, 2012 at 8:35 AM, Iasonas Lamprianou <lamprianou@> > wrote: >>> >>> Dear all, >>>> >>>> I run a kruskal wallis test and found significant results. Then, I > conducted all pairwise comparisons and found no significant results. Could > anyone please give me a hint as to why this happens or redirect me towards a > specific web page where I can find more info? (I used alpha=5% and made no > bonferroni or other correction for the pairwise comparisons) >>>> Thank you >>>> >>>> >>>> Dr. Iasonas Lamprianou >>>> Department of Social and Political Sciences >>>> University of Cyprus >>>> [[alternative HTML version deleted]] >>>> >>>> >>>> ______________________________________________ >>>> R-help@ mailing list >>>> https://stat.ethz.ch/mailman/listinfo/r-help >>>> PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html >>>> and provide commented, minimal, self-contained, reproducible code. >>>> >>>> >>> >>> >>> >> [[alternative HTML version deleted]] >> >> >> ______________________________________________ >> R-help@ mailing list >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide >> http://www.R-project.org/posting-guide.html >> and provide commented, minimal, self-contained, reproducible code. >> > > > ----- > Frank Harrell > Department of Biostatistics, Vanderbilt University > -- > View this message in context: > http://r.789695.n4.nabble.com/kruskal-wallis-post-hoc-tp4288008p4288894.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. -- Peter Dalgaard, Professor, Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Email: pd....@cbs.dk Priv: pda...@gmail.com ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.