RE: BOV

From: "Wang, Yaning" WangYA@cder.fda.gov Subject: RE: [NMusers] BOV Date: Wed, September 22, 2004 10:50 pm Micheal: I was using "occasion" loosely in my original hospital/region example. In that example, occasion is referring to site. Just think of occasion as a factor, whatever it is. ("You can never step into the same river twice" Can I use this to argue that time change also means location change?^_^). This should explain your first 3 comments. For your last comment, my intention was that IF we want to estimate BOVj we SHOULD have more occasions (replicates) because there is no replicates for occasion in the original design (well, this turned out to be wrong. We don't need to have replicates for occasion). To make the concept of occasion more lucid, let me use Ken's example to explain my personal understanding of BOV. In Ken's example, different BOV is assumed for two periods, BOV1 for weeks 1 & 2 (month1) vs BOV2 for weeks 26 & 27 (month 6). In my terms, period (or month) is the first-level occasion. But occasion in BOV1 or BOV2 is not referring to month, but week (the second level of occasion). My original thought was that in order to estimate BOV1, a subject needs to have more than one CL measured in month1, e.g. one in week1 and another in week2. But that does not seem to be necessay as long as many subjects have one CL measured in week1 (similar to the simulation done by Matts and Nick). In Ken's simulation, he had 3 CL measurements in one week (week1 or week2 but not across weeks/occasions in period 1 or month1) and another 3 CL measurements in another week (week26 or week27 but not across weeks/occasions in period 2 or month6) for each subject. The 3 replicates teased out the measurement errors. Anyway, I am sorry that I might have made it more confusing. Yaning Wang, PhD Pharmacometrician OCPB, CDER, FDA