increasing ETA estimates with adding full block

From: r.vanhest@erasmusmc.nl Subject: [NMusers] increasing ETA estimates with adding full block Date:8/18/2003 2:29 AM Dear NONMEM users, In having built a two compartment model with first order absorption, lag time and several covariates on V2 and CL, I ran into the following problem. When adding a full BLOCK in the OMEGA matrix to the final model the objectiove function significantly decreases (more than 100 points). However, the estimates for ETA (IIV and BOV) clearly increase. For example the ETA for KA increases from 111% to 126% and the ETA for V2 from 82% to 101%. So I seem to explain less inter-subject variability with adding a full block. Does someone has an explanation for this and knows how to deal with this? Thanks in advance, Reinier van Hest Research Pharmacist Department of Pharmacy Erasmus MC University Medical Centre Rotterdam P.O. Box 2040 3000 CA Rotterdam Tel: +31 10 4633202 Fax: +31 10 4636605 e-mail: r.vanhest@erasmusmc.nl