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RE: change calculation of WRES?

From: R.ter.Heine
Date: Tue, 25 Aug 2009 14:57:07 +0200

Dear Nele,
 
Couldn't this be solved by simply turning on a flag after a certain time =
and estimate a seperate residual error when this flag is turned on? Ofcou=
rse you can also code this flag in your dataset.
 
Rob
 
 
 
 

________________________________

Van: owner-nmusers
amens nele.kaessner
Verzonden: dinsdag 25 augustus 2009 14:21
Aan: nmusers
Onderwerp: [NMusers] change calculation of WRES?



Dear nmusers,

I have a question which I hope is not too trivial for the group. I am cur=
rently analyzing some data where I have more trust in values at late time=
 points. Therefore, I would like WRES to be a function of time, putting=
 more weight on late time points. In the help guide I found that WRES c=
an be influenced by SPTWO, however no real documentation exists (or I am =
not aware of it) about how to use it. Does anybody have an example for me=
 of how to code this?
Moreover, I noticed that no matter how I describe my weighting for IWRES,=
 this does not at all seem to influence my objective function or parame=
ter values. When evaluating a model, most people consider anyway that WR=
ES is what counts, as IWRES are in most cases ok anyway. So my very simpl=
e question is: If this does not influence any of this and I don't use IWR=
ES to decide if a model is good or bad, why bother at all to calculate th=
em? I noticed that the standard errors seem to change depending on which =
weighting I use for IWRES. Can anybody explain this?

Thanks and best wishes
Nele
______________________________________________________________

Dr. Nele Kner
Pharmacometrics -- Modeling and Simulation

Nycomed GmbH
Byk-Gulden-Str. 2
D-78467 Konstanz, Germany

Fon: (+49) 7531 / 84 - 4759
Fax: (+49) 7531 / 84 - 94759

mailto: nele.kaessner
http://www.nycomed.com

County Court: Freiburg, Commercial Register HRB 701257
Chairman Supervisory Board: Charles Depasse
Management Board: Dr. Barthold Piening, Gilbert Rademacher, Dr. Anders Ul=
lman





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Received on Tue Aug 25 2009 - 08:57:07 EDT

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