Obermeier Andrew <andrewobermeier <at> me.com> writes: > Hello, I just joined this list today, so am worried about proper > protocol, but would like to post a question about lme4.
You should probably join/post this question to the r-sig-mixed-models <at> r-project.org mailing list, which is specialized for those topics. > In Baayen, Davidson, and Bates (2008), Mixed-effects modeling with > crossed random effects for subjects and items, the authors describe > steps for a Latin Square Design (p. 402) in which they compare 3 > levels of the experimental conditions. I am considering replicating > this analysis for my dissertation, I would also like to investigate > 3 levels of my factor, but wish to confirm how lme4 derives the t > value. > It is my understanding that t values can only be used to compare 2 > means. For 3 levels, does lme4 do some kind of pairwise comparison? If you want to do a single test of the effect of a three-level factor (i.e. compare otherwise identical models with and without the factor), then the canonical approach is to do some kind of model comparison test (likelihood ratio test, conditional F test, etc.). This is a little bit of a can of worms in the case where the number of groups is small enough that we would like to take the finite sample size into account (i.e. we would prefer a conditional F test to the LRT, but we don't know the denominator degrees of freedom). You might want to look at Doug Bates's book draft at http://lme4.r-forge.r-project.org/lMMwR/ or at http://glmm.wikidot.com/faq ... ______________________________________________ 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.
