RE: How sparse is too sparse?

From: "Kowalski, Ken" Ken.Kowalski@pfizer.com Subject: RE:[NMusers] How sparse is too sparse? Date: Fri, June 11, 2004 8:10 am Serge, I can certainly understand that Robert won't be able to separate out intra-individual variability in the PK parameters with only 1 obs/visit (i.e., inter-occasion or between-visit variability within a subject). But he should be able to separate out intra-individual variability in the response (i.e., measurement variability or sigma^2) from the inter-individual variability in the PK parameters since he is getting two measurements on each individual (one measurement on each of two visits). Of course if there is true inter-occasion variability it will be confounded with other sources and most likely will inflate the intra-individual variability in the measured response (sigma^2). Ken _______________________________________________________