Hi there, I'm trying to fit GEE models on binomial data. My problem is how to "select" a model if ever it is possible and how I decide a factor has to be drop out or not. More specifically: 1) Are QIC (Pan 2001) reliable and can be used in a model selection framework (Burhnam and Anderson 1998)? If yes, how can the QIC be estimated from available information in a gee object? 2) If not, can R compute an ANOVA table like for GLM (seems that SAS does it)? The problem is to know whether a factor with more than 2 levels is significant or not. Can I consider such a factor as significant if at least one modality (using a Wald-test) is significant? 3) Some models can be fitted with a gml but not with a gee? Is there any explanation for that? Any answer would be greatly appreciated, Christophe ------------------------------------------------------------------------ Bonenfant Christophe Laboratoire de Biom??trie et Biologie Evolutive UMR CNRS 5558 - Universit?? Claude Bernard Lyon 1 43, Boulevard du 11 Novembre 1918 F-69622 Villeurbanne Cedex T??l: 04-72-44-81-11 Mobile: 06-62-11-20-00 Courriel: bonenfan at biomserv.univ-lyon1.fr In Tartiflette we trust...