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RE: Simulations with/without residual error

From: Grevel, Joachim <Joachim.Grevel>
Date: Tue, 7 Jul 2009 11:35:55 +0100

Dear NMUsers,
I cannot see a reason to leave out the residual error. We all know how =
error shifts around between IIV, IOV, and residual error. A large =
residual error is indeed troublesome even when all other model =
parameters would indicate a good fit with small shrinkage. You only =
recognize the trouble when you start simulating the kind of responses =
listed by Andreas. You may have to conclude in the end that your model =
is not very predictive because of large residual error (=large, still =
unexplained variability).
Joachim Grevel
AstraZeneca R&D Charnwood
Clin. Pharmacology and DMPK
Bakewell Road
Loughborough, LE11 5RH
Tel: +44 1509 64 5177

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-----Original Message-----
From: owner-nmusers
Sent: 07 July 2009 10:34
To: nmusers
Subject: [NMusers] Simulations with/without residual error



The recent discussion about simulation with a nonparametric method =
brought a general question concerning monte-carlo simulations into my =
mind. When should simulations be performed with residual error and when =
not. I am especially interested in comments regarding the following =
scenarios when the result of the simulation should be reported as mean =
or median and 90% prediction interval:

1. Simulated response at a particular time point (eg. Trough values)

2. Simulated response at a particular time point (x) relative to =
baseline response (IPRED(t=x)/IPRED(t=0) vs. DV(t=x)/DV(t=0) )

3. Simulated time of maximal response (eg. Tmax)



Thanks and best regards, Andreas.





Andreas Lindauer


Department of Clinical Pharmacy

Institute of Pharmacy

University of Bonn

An der Immenburg 4

D-53121 Bonn


phone: + 49 228 73 5781

fax: + 49 228 73 9757


Received on Tue Jul 07 2009 - 06:35:55 EDT

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