Re: Describing variability

From: Nick Holford Subject:Re: [NMusers] Describing variability Date:Fri, 28 Mar 2003 10:12:27 +1200 Justin, Atul, I would suggest you always add the between occasion variability to your model before searching for fixed effect covariates (e.g. healthy vs patient). The seminal paper by Karlsson & Sheiner pointed out "Our simulations show that neglecting IOV can cause significant bias in any of the fixed-effect population parameter estimates". Karlsson MO, Sheiner LB. The importance of modeling interoccasion variability in population pharmacokinetic analyses. Journal of Pharmacokinetics & Biopharmaceutics 1993; 21(6):735-50. -- 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/