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Re: [NMusers] nonmem question regarding condition number

From: Sven Mensing <sv.mensing_at_gmail.com>
Date: Thu, 24 Mar 2016 13:41:59 +0100

Hi Lauren,

my first guess would be that you do not need as many ETAs as you had before
when using 3 compartments. May you also added TAs on the 3rd compartments'
parameter? Either way, please check for overparametrization as Caroline
indicated, perferably starting with the ETAs.

Kind regards

Sven Mensing

2016-03-24 11:10 GMT+01:00 L.A. ten Berg - Lammers <
l.a.tenberg-lammers_at_amc.uva.nl>:

> Dear nmusers,
> I am currently analyzing PK profiles after a single iv adminstration.
> Volunteers were sampled frequently: 12 samples per curve.
> For the structural model 2- and a 3-compartment models are compared. The
> CWRES vs time plot of the 2-compartment shows the typical wave, indicative
> for a 3-compartment model. Introduction of a third compartment eliminated
> the wave, OFV decreased with 180 points, precision of the estimates did
> change notably, but the condition number increased from 998 to 2.0*E16.
> Does anyone know how to interpret this large increase in condition number?
> Best wishes,
> Laureen ten Berg
>
>
>
> *[image: Beschrijving: cid:image001.gif_at_01CD804B.C9EE1BA0]*
>
>
>
>
>
> *Laureen ten Berg-Lammers*
>
> Hospital Pharmacist
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> Academisch Medisch Centrum
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> Universiteit van Amsterdam
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> Meibergdreef 9 | 1105 AZ Amsterdam | Room: M01-224
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> Tel: +31(0)20-5662726 | Pager *62726 | *l.a.tenberg-lammers_at_uva.amc.nl
> <l.a.tenberg-lammers_at_uva.amc.nl>*
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Received on Thu Mar 24 2016 - 08:41:59 EDT

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