RE: modeling interoccasion variability

From: Nick Holford n.holford@auckland.ac.nz Subject: RE: [NMusers] modeling interoccasion variability Date: 11/18/2003 1:17 PM Carl, It sounds like you should be using the SAME option: "instead of having a measure of variability for each of the 10 occasions separately, I would like to have a single overall measure of variability for the IOV for clearance" This means that you only estimate one OMEGA which is the same for all occasions. The ETA for each occasion will be different because they are sampled from a different distribution with the SAME variance. I don't know of any intrinsic reason why having different numbers of occasions for your subjects should make it hard to estimate BOV (between occasion variability aka IOV). Here is an example showing how to code this for NM-TRAN: $OMEGA .5 ; BSVCL $OMEGA BLOCK(1) .1 ; BOVCL1 $OMEGA BLOCK(1) SAME ;; BOVCL2 ... $OMEGA BLOCK(1) SAME ;; BOVCLn $PK IF (OCC.EQ.1) THEN BOVCL=ETA(2) ENDIF IF (OCC.EQ.2) THEN BOVCL=ETA(3) ENDIF ... IF (OCC.EQ.n) THEN BOVCL=ETA(n+1) ENDIF CL=POPCL*EXP(ETA(1) + BOVCL) -- 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/ _______________________________________________________