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RE: OMEGA BLOCK with mixture model?

From: Stephen Duffull <stephen.duffull>
Date: Thu, 16 Apr 2009 20:13:00 +1200


> With oral data only I would normally model with BLOCK(2) on
> CL/F and V/F or a DIAG(3) on CL/F, V/F and relative F. The
> latter may have some advantages for diagnostics, covariate
> model building etc.

I have often seen these two options considered. I am unclear as to the adv=
antages of DIAG(3) over BLOCK(2)? In theory it would seem that they should=
 be identical. In practice it seems that DIAG(3) is more relaxed since it =
is not required that the variance of relative F if reassigned to the covari=
ance of (CL/F, V/F) [under BLOCK(2)] yields a positive definite matrix.

I presume an advantage wrt covariate model building would be access to the =
EBEs of F_i. However, given the variance of F_i may exceed the covariance =
of (CL/F, V/F) then I wonder if this is a real advantage or an artefact of =
numerical procedures?

I am keen to learn more about real advantages of application of DIAG(3) as =
an alternative to BLOCK(2).

Professor Stephen Duffull
Chair of Clinical Pharmacy
School of Pharmacy
University of Otago
PO Box 913 Dunedin
New Zealand
E: stephen.duffull
P: +64 3 479 5044
F: +64 3 479 7034

Design software:
Received on Thu Apr 16 2009 - 04:13:00 EDT

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