This is not the best place for this post. Post instead to r-sig-mixed-models or r-sig-ecology .
Cheers, Bert On Thu, Jul 11, 2013 at 8:48 AM, Linda Bürgi <patili_bue...@thotmail.com> wrote: > > > > > Dear All, > > I have two quick questions about my study design. For 4 years, once every > season, we destructively sampled larvae on bushes (the same bushes every > time) and measured parasitism on these larvae. We had 10 bushes per location > and two locations. > We are interested in whether parasitism changed over the years and varied > with season. With repeated measures on bushes, and bushes nested in location, > my model looks like this: > > model<-glmmPQL(parasitism ~ year:season + year + season, > random=~1|location/bush, family=binomial) > > Question 1: A reviewer of our paper suggested that seasons are nested > within years and that we should include this in the model. However, I > think seasons are crossed with years, not nested. If that's the case, > can I leave the model as is (as far as season and years are concerned)? > > Question 2: I know it is ridiculous to have location as a random factor since > it only has two levels. I've read a lot in the archives and people usually > suggest to leave that factor out altogether. But leaving it out is not an > option because levels of parasitism > vary significantly with location (but that is of no interest to us, > hence not really a fixed factor). Could I just include it as a covariate? > glmmPQL(parasitism ~ year:season + year + season + location, random=~1|bush, > family=binomial)? > > Thank you already for any answers and suggestions! > > PS. I used glmmPQL instead of lmer because without the over-/underdispersion > function in lmer everything was highly significant, whereas with glmmPQL it > is not. > > > > [[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. -- Bert Gunter Genentech Nonclinical Biostatistics Internal Contact Info: Phone: 467-7374 Website: http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm ______________________________________________ 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.
