nonmem question regarding condition number

Dear nmusers, I am currently analyzing PK profiles after a single iv adminstration. Volunteers were sampled frequently: 12 samples per curve. For the structural model 2- and a 3-compartment models are compared. The CWRES vs time plot of the 2-compartment shows the typical wave, indicative for a 3-compartment model. Introduction of a third compartment eliminated the wave, OFV decreased with 180 points, precision of the estimates did change notably, but the condition number increased from 998 to 2.0*E16. Does anyone know how to interpret this large increase in condition number? Best wishes, Laureen ten Berg [Beschrijving: cid:[email protected]] Laureen ten Berg-Lammers Hospital Pharmacist Academisch Medisch Centrum Universiteit van Amsterdam Meibergdreef 9 | 1105 AZ Amsterdam | Room: M01-224 Tel: +31(0)20-5662726 | Pager *62726 | [email protected] ________________________________ AMC Disclaimer : https://www.amc.nl/disclaimer ________________________________