Thanks everyone. I will be using the empirical procedure option with a spatial covariance random effect which fits a GEE-type model. In that case, likelihood estimation is not used and likelihood based fit statistics are not returned. Instead, pseudo-likelihood takes its place, which from the SAS documentation disallows model comparison using things like pseudo-AIC, and by extension I would assume would disallow likelihood ratio tests involving the full and reduced models. If I were to use a contrast statement with random effects, am I correct to assume that the spatial covariance structure used in the contrasts are those from the full model? Otherwise, the model would need to be fit twice. When fit separately, the full (with interaction) and reduced models have slightly different covariance structures. Is this a potential issue with a fix by setting some procedure options?
Seth