Subject: Re: question for aov and kruskal Newsgroups: R-help:gmane.comp.lang.r.general To: eugen pircalabelu <[EMAIL PROTECTED]>
On 10 Mar 2008, you wrote in gmane.comp.lang.r.general: > Hi R users! > > I have the following problem: how appropriate is my aov model under > the violation of anova assumptions? > > Example: > a<-c(1,1,1,1,1,1,1,1,1,1,2,2,2,3,3,3,3,3,3,3) > b<-c(101,1010,200,300,400, 202, 121, 234, 55,555,66,76,88,34,239, > 30, 40, 50,50,60) z<-data.frame(a, b) > fligner.test(z$b, factor(z$a)) > aov(z$b~factor(z$a))->ll > TukeyHSD(ll) > > Now from the aov i found that my model is unbalanced, and from the > flinger test i found out that the assumption of homogeneity of > variances is rejected. Could my Tukey comparison be a valid one > under these violations? From what i read the Tukey test is valid > only when the model is balanced and when the assumption of > homogeneity of variances is not rejected, am i wrong? Can anyone > tell me what would be the correct test in this case? > > Doing a non-parametric Kruskal - wallis test would give me a > different result. But what would be the correct multiple comparison > test in this case? > If you install the coin package and look at ?oneway_test help panel, you will see an implementation of what the authors (citing Hollander and Wolfe) are calling the Nemenyi-Damico-Wolfe-Dunn test. From the example it appears that you also need the multcomp package to run the test. -- David Winsemius ______________________________________________ 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.
