RE: BOV

From: "Wang, Yaning" WangYA@cder.fda.gov Subject: RE: [NMusers] BOV Date: Wed, September 22, 2004 2:08 pm Micheal: Occasion could be either location or time period. The hospital/region example is used to simply the problem and explain a concept. In fact, anything in sequence is confounded with time. Let's use time period as the occasion (e.g. in a crossover experiment). Suppose the whole experiment is conducted in one hospital and there are 4 periods. Analogous to my previous example, in the simple scenario(same BOV in all occasions), BOV is just the within-subject variance across periods. In the complex scenario (different BOV in all occasions), the interpretation will be different. Basically we assume different variance at each period, say, BOV1<BOV2<BOV3<BOV4. What is the between-occasion here? It is not between period 1, period 2, period 3 and period 4. It is between period1(in this current experiment) and period1' (if we can repeat the whole crossover experiment) for BOV1. This second level of between-occasion in this case is nothing but the true measurement error (replicates within a subject for the same period). Here period 1 in the current experiment is analogous to the hospital in New York. Period 1 in the current experiment and period1' in a repeated experiment are two hospitals in New York. Yaning Wang, PhD Pharmacometrician