RE: bias and good fit vs centering

From: "Wang, Yaning" WangYA@cder.fda.gov Subject: RE: [NMusers] bias and good fit vs centering Date: Fri, 19 Aug 2005 09:55:43 -0400 Pavel: If your residual error model is not additive (Y=F+ERR(1)), I would rather use FOCE with interaction (METHOD=1 INT) instead of LAPLACIAN. In the current version of NONMEM (version V), LAPLACIAN ignore the interaction between ETA and EPSILON when it does exit. If you have a model like Y=F(eta)+F(eta)*ERR(1), LAPLACIAN will first simplify the model to Y=F(eta)+F(0)*ERR(1) and then move on. In my opinion, for a linear mixed model with a proportional error model, LAPLACIAN is equal to FO. Despite the better approximation of LAPLACIAN method for the marginal likelihood in general, lack of interaction option for LAPLACIAN may ultimately make LAPLACIAN worse than FOCE with interaction when the residual error model includes an interaction. Yaning Wang, Ph.D. Pharmacometrician Office of Clinical Pharmacology and Biopharmaceutics Center of Drug Research and Evaluation Food and Drug Administration Office: 301-827-9763