RE: Negative values in 95%CI on ETAs

From: "Nick Holford" n.holford@auckland.ac.nz Subject: RE: [NMusers] Negative values in 95%CI on ETAs Date: Thu, November 25, 2004 4:20 am Manoj, The inclusion of a negative value in the 95% CI for an estimate of OMEGA arises from the assumptions that 1) NONMEM is correctly computing the standard error 2) the uncertainty distribution for the parameter is symmetrical. Both of these assumptions can be sidestepped by constructing a bootstrap distribution of the estimates (see http://wfn.sourceforge.net for some details). This is a good idea for any parameter estimated by NONMEM. IMHO any 95% CI constructed using the asymptotic SE from NONMEM is suspect. Nick -- Nick Holford, Dept Pharmacology & Clinical Pharmacology University of Auckland, 85 Park Rd, Private Bag 92019, Auckland, New Zealand email:n.holford@auckland.ac.nz tel:+64(9)373-7599x86730 fax:373-7556 http://www.health.auckland.ac.nz/pharmacology/staff/nholford/ _______________________________________________________