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[NMusers] RE: nonmem question regarding condition number

From: Eleveld-Ufkes, DJ <d.j.eleveld_at_umcg.nl>
Date: Thu, 24 Mar 2016 12:56:59 +0000

Hi Laureen,
If you want an objective second opinion then make likelihood profiles for b=
oth models.
I expect a very shallow one for at least one maybe two parameters for the 3=
-compartment model and thus the parameters are not estimated accurately, ev=
en if the objective function goes down.
good luck,
Douglas Eleveld
________________________________
From: owner-nmusers_at_globomaxnm.com [owner-nmusers_at_globomaxnm.com] on behalf=
 of L.A. ten Berg - Lammers [l.a.tenberg-lammers_at_amc.uva.nl]
Sent: Thursday, March 24, 2016 11:10 AM
To: 'nmusers_at_globomaxnm.com'
Subject: [NMusers] nonmem question regarding condition number

Dear nmusers,
I am currently analyzing PK profiles after a single iv adminstration. Volun=
teers were sampled frequently: 12 samples per curve.
For the structural model 2- and a 3-compartment models are compared. The CW=
RES vs time plot of the 2-compartment shows the typical wave, indicative fo=
r 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


[Beschrijving: cid:image001.gif_at_01CD804B.C9EE1BA0]




Laureen ten Berg-Lammers

    Hospital Pharmacist


Academisch Medisch Centrum
Universiteit van Amsterdam




Meibergdreef 9 | 1105 AZ Amsterdam | Room: M01-224
Tel: +31(0)20-5662726 | Pager *62726 | l.a.tenberg-lammers_at_uva.amc.nl




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Received on Thu Mar 24 2016 - 08:56:59 EDT

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