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unprecise estimation

From: Chiaying Lin <cylin292>
Date: Tue, 8 Sep 2015 22:36:23 +0800

Dear NMusers,
I'm a NM beginner modeling for a monoclonal antibody. Below is 12
subjects's individual predicted plot , it seems that nonlinear
elimination (Michaelis-Menten) model can fit the data well. However, when
running the control stream (two compartment models with linear and
non-linear elimination), the resulting Q THETA SE% and OMEGA SE% are quite
large even thought successful minimization.From the Correlation Matrix , I
find that THETA (1) (VMAX) and THETA(2) (KM)are highly correlated (9.67E-01).
Another problem is the .fit file can't be produced.

I have tried various error models and initial estimations, however, none
had better improvement and often got error message (error 134
or parameter estimate is near its boundary). Does re-parameterization
helpful ? or need to change to other models?

Any suggestions for solving the problems are highly appreciated.

(control stream will be send in another e-mail)

Received on Tue Sep 08 2015 - 10:36:23 EDT

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