Significance?

From: chyihung.hsu@pharma.novartis.com Subject: [NMusers] Significance? Date: Tue, 2 Apr 2002 16:56:12 -0400 Dear NONMEM users, I am fitting a 3-comp. population model to a data set. Based on the base model (model without any covariate), significant differences in post-hoc estimates of CL and their corresponding etas were suggested between 2 groups of subjects (Groups A and B). But adding the grouping covariate to the TVCL part of the base model did not seem to help, and the coefficient and the reduction in OBJ were far from statistical significance. On the contrary, this agreed with previous diagnostic and non-compartmental results. Should significant coefficient be expected? any suggestions? Thanks in advance. Best regards, Chyi-Hung Additional data and model information: Data: intensive samples. Model: random effects: CL,V1,Q2, and V2 were assumed to be log-normally distributed, with var-cov matrix=block(block(CL,V1), block(V2,Q2)), error = additive + multiplicative, and V2 > V3. Estimation: CONDITIONAL INTERACTION.