NONMEM vs SPSS

Dear NONMEM Users Does anyone have a view on the relative merits/reliability/accuracy of NONMEM ($COV step) vs SPSS (NLR) with respect to their derived values of the parameter standard errors and parameter correlation matrices? The data I am analysing are single subject (not population). Parameter estimates from the two programs are, to all intents and purposes, identical. However, the SE values from NONMEM $COV are consistently smaller by 1.5-2.0-fold. Any thoughts? Gavin __________________________________________________ Dr Gavin E Jarvis MA PhD VetMB MRCVS University Lecturer in Veterinary Anatomy Department of Physiology, Development & Neuroscience Physiological Laboratory Downing Street Cambridge CB2 3EG Tel: +44 (0) 1223 333745 Fellow and College Lecturer in Pharmacology Selwyn College Cambridge CB3 9DQ Tel: +44 (0) 1223 761303 Email: <mailto:[email protected]> [email protected] Web: http://www.pdn.cam.ac.uk/staff/jarvis www.pdn.cam.ac.uk/staff/jarvis Twit: @GavinEJarvis