RE: Centering (was Re: Missing covariates)

From: "Gibiansky, Leonid" <gibianskyl@globomax.com> Subject: RE: Centering (was Re: Missing covariates) Date: Thu, 5 Jul 2001 10:29:52 -0400 I think the answer to the question 1 depend on your error model. For additive error model, the model predicts mean: If Y=F+EPS1 then F=mean(Y) For proportional - geometric mean. If Y=F*EXP(EPS1) then F=geomean(Y) For combined - I am not quite sure, it should be possible to study based on the simple examples above. Answer to question 2 depend on your goal. You have a model for everyone. So it is your call whether you want to predict CL for the person with mean weight or median weight, for males or females, etc. I am not sure that model with covariates can be simply reduced to the base model. These are different statistical models, based on different assumptions. I would not try to derive base model from the covariate model. Leonid