Hi Karin, You could use a gls method and look at the distribution of your residuals. It is the residuals which must be normally distributed, which can be checked using diagnostic plots such as a histogram or qq-plot of the residuals of your model.
Cheers Alejandro On 30, May 2012, at 4:12 PM, Karin Schneeberger wrote: > Dear all > > I'm trying to compare one trait across three (unordered categorical) groups > including 25 species (let's say for example basal metabolic rate of aquatic, > terrestrial and aerial mammals). > > If the data would be normally distributed, I would simply use a phylogenetic > ANOVA including a post-hoc test on means accounting for the phylogeny, as > provided by the package "phytools". However, my tip-data are far away from > being normally distributed, and transformations only lead to unsatisfying > improvements (e.g Shapiro-Wilk test returns a p-Value of 0.08 instead of 0.03 > as before transformation). So I am not convinced that a phylogenetic ANOVA is > the right approach for dealing with these sort of data. > Is there any non-parametric approach to compare groups across phylogeny that > also returns which groups differ from each other? > > Your sincerely, > Karin > > [[alternative HTML version deleted]] > > _______________________________________________ > R-sig-phylo mailing list > R-sig-phylo@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-phylo __________________________________ Alejandro Gonzalez Voyer Post-doc Estación Biológica de Doñana Consejo Superior de Investigaciones Científicas (CSIC) Av Américo Vespucio s/n 41092 Sevilla Spain Tel: + 34 - 954 466700, ext 1749 E-mail: alejandro.gonza...@ebd.csic.es Web site (Under construction): Personal page: http://consevol.org/members/alejandro.html Group page: http://consevol.org/index.html For PDF copies of papers see: http://csic.academia.edu/AlejandroGonzalezVoyer [[alternative HTML version deleted]]
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