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Re: PARAMETER ESTIMATE IS NEAR ITS BOUNDARY with NONMEM v6

From: Nick Holford <n.holford>
Date: Fri, 25 Sep 2009 08:30:24 +1200

Chandra,

Please post your control stream that causes the warning. I wonder how
you are dealing with the one obs/animal problem.

My advice on how to handle the warning is to look at the parameter
estimates and ask yourself if they seem sensible. Interpretation of
boundaries is up to the user and his/her knowledge of the underlying
problem.

Nick

Durairaj Chandrasekar wrote:
> Dear group,
>
> Recently I was running a sparse sampling animal data (one data per animal) using NONMEM v6 & WFN and ran into this trouble:
>
> "PARAMETER ESTIMATE IS NEAR ITS BOUNDARY
> THIS MUST BE ADDRESSED BEFORE THE COVARIANCE STEP CAN BE IMPLEMENTED".
>
> I searched the forum for any solution and found the message from Mark Sale (Next Level Solutions).
>
> My question: a) Is there any option to overcome this issue without suppressing the message as suggested earlier?
> b) What causes the above problem? Do I need to avoid specifying any boundary for the thetas?
> c) What does this message indicate? a poor selection of model? poor initial estimates? narrow boundary? or any correlation issues with the estimates?
>
> I highly appreciate your input. Thanks in advance
>
> Regards,
> Chandra Durairaj,
> Post-doctoral Fellow,
> Univ of Colorado Denver
>
>
>
>

--
Nick Holford, Professor Clinical Pharmacology
Dept Pharmacology & Clinical Pharmacology
University of Auckland, 85 Park Rd, Private Bag 92019, Auckland, New Zealand
n.holford
mobile: +64 21 46 23 53
http://www.fmhs.auckland.ac.nz/sms/pharmacology/holford
Received on Thu Sep 24 2009 - 16:30:24 EDT

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