On Wed, 9 Apr 2008, João Fadista wrote: > But in that paper they refer to another > (http://www.bepress.com/cgi/viewcontent.cgi?article=1053&context=ucbbiostat) > where they say that "permutation distribution produces an asymptotically > correct null distribution if (i) the sample sizes are equal...".
I haven't read that paper in detail (but so do you, it seems). From looking at abstract and intro, my understanding is that they also study the behaviour of tests under weaker assumptions than exchangeability. Z > Best regards, > João > > ________________________________ > > De: Achim Zeileis [mailto:[EMAIL PROTECTED] > Enviada: qua 09-04-2008 0:26 > Para: João Fadista > Cc: ONKELINX, Thierry; r-help@r-project.org > Assunto: Re: [R] permutation test assumption? > > > > On Wed, 9 Apr 2008, João Fadista wrote: > > > Dear Thierry, > > > > Thanks for the reply. But as you may read in the paper > > http://bioinformatics.oxfordjournals.org/cgi/content/abstract/22/18/2244 > > when the sample sizes are not the same there may be an increase in the > > Type I error rate. > > No, this is false and not what the reference above says. Please read more > carefully. > > > Comments will be appreciated. > > The basic assumption for permutation tests is exchangeability of the > observations (regardless of sample sizes). The reference above describes a > situation when this assumption is violated. > Z > > > Best regards, > > João Fadista > > > > > > ________________________________ > > > > De: ONKELINX, Thierry [mailto:[EMAIL PROTECTED] > > Enviada: ter 08-04-2008 15:27 > > Para: João Fadista; r-help@r-project.org > > Assunto: RE: [R] permutation test assumption? > > > > > > > > Dear João, > > > > You can do permutation tests on an unbalanced design. > > > > HTH, > > > > Thierry > > > > > > ---------------------------------------------------------------------------- > > ir. Thierry Onkelinx > > Instituut voor natuur- en bosonderzoek / Research Institute for Nature and > > Forest > > Cel biometrie, methodologie en kwaliteitszorg / Section biometrics, > > methodology and quality assurance > > Gaverstraat 4 > > 9500 Geraardsbergen > > Belgium > > tel. + 32 54/436 185 > > [EMAIL PROTECTED] > > www.inbo.be > > > > To call in the statistician after the experiment is done may be no more > > than asking him to perform a post-mortem examination: he may be able to say > > what the experiment died of. > > ~ Sir Ronald Aylmer Fisher > > > > The plural of anecdote is not data. > > ~ Roger Brinner > > > > The combination of some data and an aching desire for an answer does not > > ensure that a reasonable answer can be extracted from a given body of data. > > ~ John Tukey > > > > -----Oorspronkelijk bericht----- > > Van: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Namens João Fadista > > Verzonden: dinsdag 8 april 2008 15:18 > > Aan: r-help@r-project.org > > Onderwerp: [R] permutation test assumption? > > > > Dear all, > > > > Can I do a permutation test if the number of individuals in one group is > > much bigger than in the other group? I searched the literature but I > > didin´t find any assumption that refers to this subject for permutation > > tests. > > > > > > Best regards > > > > João Fadista > > Ph.d. student > > > > > > > > UNIVERSITY OF AARHUS > > Faculty of Agricultural Sciences > > Dept. of Genetics and Biotechnology > > Blichers Allé 20, P.O. BOX 50 > > DK-8830 Tjele > > > > Phone: +45 8999 1900 > > Direct: +45 8999 1900 > > E-mail: [EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]> > > Web: www.agrsci.org <http://www.agrsci.org/> > > ________________________________ > > > > DJF now offers new degree programmes > > <http://www.agrsci.org/content/view/full/34133> . > > > > News and news media <http://www.agrsci.org/navigation/nyheder_og_presse> . > > > > This email may contain information that is confidential. Any use or > > publication of this email without written permission from Faculty of > > Agricultural Sciences is not allowed. If you are not the intended > > recipient, please notify Faculty of Agricultural Sciences immediately and > > delete this email. > > > > > > > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > 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. > > > > > > > > > ______________________________________________ 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.
