covariate significance

From: "Joern Loetsch" Subject: [NMusers] covariate significance Date: Thu, 18 Apr 2002 20:44:25 +0200 Dear NONMEM users, say there is a covariate "COV" that can take the values of 0, 1 or 2 (nothing else). There is a parameter X to which the covariate is connected by either (choice 1) IF (COV.EQ.0) THEN X=THETA(1) ELSE X=THETA(1)*THETA(2) ENDIF or (choice 2) IF (COV.EQ.0) THEN X=THETA(1) ELSE X=THETA(1)*THETA(2)*COV ENDIF Would one go with the second choice when the fit is simply better or only when the objective function decreases significantly as compared to choice 1. I'm not in clear because it looks to me as if both choices had the same number of parameters. Thanks in advance Jorn ______________________________________________________ Jorn Lotsch, MD pharmazentrum frankfurt, Dept. of Clinical Pharmacology Johann Wolfgang Goethe-University Hospital Theodor-Stern-Kai 7 D-60590 Frankfurt am Main GERMANY Tel.:+49-69-6301-4589 Fax.:+49-69-6301-7636 http://www.klinik.uni-frankfurt.de/zpharm/klin/