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RE: Models that abort before convergence Addendum

From: Mark Sale - Next Level Solutions <mark>
Date: Fri, 21 Nov 2008 12:09:58 -0700
  Let me understand:
You now have a theor= y that the way to determine whether the NONMEM error messages are useful (i= .e., they tell you something about the model "goodness") is a poll.  T= his, I think is a theory (and one well established in epistomolgy) of how t= o find an optimal solution - appeal to a large number of presumably well in= formed people.  As data that may be relavant to this theory, I would p= oint out that a poll gave us GW Bush as our 43rd president.
 Nick, = in contrast has suggested that the error messages could be used as a source= of random numbers.   This also, I think, is a theory without dat= a to support or contradict it.
  So ....
 Let me propose a= solution - let's generate some data.  Suppose we randomly generate 10= 00 models.  We could tests the hypotheses:

Are the error messag= es random (I suspect they are not, that there is some information in them).=   To test this, see if the error messages are predictive of other (pre= sumably non-random) measure of goodness - NPC and NPDE, and perhaps PPC com= e to mind.

Do the error messages provide information not readily ava= ilable in NPC, NPDE and PPC.
Not really sure how to test this, without s= ome "gold standard" of goodness, except perhaps to compare the different me= asures to the model that was used to simulate the data (seems like measures= based on that would be "correct" in some way??).  I need some ideas o= n this.

I can generate, run and extract results from random mode= ls (using the GA software) - I already have NPDE and PPC in it, was thinkin= g of adding NPC.

Any interest/collaborators??

Mar= k Sale MD
Next Level Solutions, LLC

-------- Original Message --------
Subject: Re: [NMusers] Models that abort before convergence Addendum
From: Leonid Gibiansky <LGibiansky Date: Thu, November 20, 2008 9:57 pm
Cc: nmusers <nmusers
Nick, Mark, and All,
We can argue indefinitely, but let me propose a poll. If you like to
participate, reply directly to me (use "reply", not "reply to all"). I
will summarize all the replies received up to the end of November. Skip the questions that you do not like to answer, write NA if the question
is not applicable. Summaries will be blinded.

1. Would you like Nonmem to stop producing all run-time (not syntax)
error/warning messages (134, 137, number of significant digits, etc.)

2. Do you remember at least one example when the run-time error message helped you to find an error in your code (YES/NO):

3. In your experience, run-time error messages allow you to detect model errors or problems quicker than it would be done without error messages: (agree/disagree)

4. Have you ever used in your report/publication ANY model that did not have $COV step completed (YES/NO):

5. Have you ever used in your report/publication ANY model that did not converge (YES/NO):

6. Have you ever used in your report/publication FINAL model that did
not have $COV step completed (YES/NO):

7. Have you ever used in your report/publication FINAL model that did
not converge (YES/NO):

8. Define yourself as novice/intermediate/experienced Nonmem user:


Leonid Gibiansky, Ph.D.
President, QuantPharm LLC
e-mail: LGibiansky at
tel: (301) 767 5566

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Received on Fri Nov 21 2008 - 14:09:58 EST

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