I have 3 questions (below). Background: I am teaching an introductory statistics course in which we are covering (among other things) repeated measures anova. This time around teaching it, we are using R for all of our computations. We are starting by covering the univariate approach to repeated measures anova.
Doing a basic repeated measures anova (univariate approach) using aov() seems straightforward (e.g.: +> myModel<-aov(myDV~myFactor+Error(Subjects/myFactor),data=myData) +> summary(myModel) Where I am currently stuck is how best to deal with the issue of the assumption of homogeneity of treatment differences (in other words, the sphericity assumption) - both how to test it in R and how to compute corrected df for the F-test if the assumption is violated. Back when I taught this course using SPSS it was relatively straightforward - we would look at Mauchly's test of sphericity - if it was significant, then we would use one of the corrected F-tests (e.g. Greenhouse-Geisser or Huynh-Feldt) that were spat out automagically by SPSS. I gather from searching the r-help archives, searching google, and searching through various books on R, that the only way of using mauchly.test() in R is on a multivariate model object (e.g. mauchly.test cannot handle an aov() object). Question 1: how do you (if you do so), test for sphericity in a repeated measures anova using R, when using aov()? (or do you test the sphericity assumption using a different method)? Question 2: Can someone point me to an example (on the web, in a book, wherever) showing how to perform a repeated measures anova using the multivariate approach in R? Question 3: Are there any existing R functions for calculating adjusted df for Greenhouse-Geisser, Huynh-Feldt (or calculating epsilon), or is it up to me to write my own function? Thanks in advance for any suggestions, -- Paul L. Gribble, Ph.D. Associate Professor Dept. Psychology The University of Western Ontario London, Ontario Canada N6A 5C2 Tel. +1 519 661 2111 x82237 Fax. +1 519 661 3961 pgrib...@uwo.ca http://gribblelab.org [[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.
