Problems with formula for highly pseudoreplicatemixed-effects system
On Thu, 17 Sep 2009, Matthias Gralle wrote:
I have been trying for some weeks to state the correct design of my experiment as a GLM formula, and have not been able to find something appropriate in Pinheiro & Bates 2000 or with any of the local R users, so I am posting it here and hope somebody can help me. In each experimental condition, described by 1) gene (10 levels, fixed, because of high interest to me) 2) species (2 levels, fixed, because of high interest) 3) day (2 levels, random) 4) replicate (2 levels per day, random), I have several thousand data points consisting of two variables: 5) FITC (level of transfection of a cell) 6) APC (antibody binding to the cell) ...pseudoreplication, and with 200000 data points in the original data set, any interaction will be
What do you mean by pseudoreplication -- repeated measures? Don't you want something like APC ~ gene + FITC + (FITC|gene) + species + (1|day) + (1|replicate), where your interest is in the random regression FITC|gene?. Alternatively/equivalently, how about testing for homogeneity of the FITC-APC (partial) correlation coefficients across 10 gene strata (what do these look like?). The latter is natural for a multigroup SEM. I hope I understand what you are talking about Cheers, David Duffy.