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PARAMETER ESTIMATE IS NEAR ITS BOUNDARY with NONMEM v6

From: Durairaj Chandrasekar <chandrasekar_drj>
Date: Thu, 24 Sep 2009 13:18:50 -0700 (PDT)

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


      
Received on Thu Sep 24 2009 - 16:18:50 EDT

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