RE: OMEGA-Block
Hello Hauke,
as always for these specific questions you need to provide us with the relevant
portions of your control stream and of your output.
Thanks for participating,
Joachim
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AstraZeneca R&D Charnwood
Clin. Pharmacology and DMPK
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Loughborough, LE11 5RH
Tel: +44 1509 644035
[email protected]
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Quoted reply history
-----Original Message-----
From: [email protected]
[mailto:[email protected]]on Behalf Of Hauke Rühs
Sent: 03 August 2009 15:07
To: [email protected]
Subject: [NMusers] OMEGA-Block
Dear NMusers,
modelling a 2-compartmet model parameterized by CL, V1, VSS and Q, I got
to a problem with which I don’t know how to deal with: After choosing my
structural and statistic model (combined residual error model) I estimated
the covariance matrix by including an OMEGA-BLOCK(4), which reduced the
OFV by 15. The correlations between the parameters were all estimated to
be minor (< 0.8). But when I model with a BLOCK(2) on VSS and V1, which I
would expect to be positively correlated, the correlation is estimated to
be -0.99. Additionally, the inclusion of BLOCK(2) does not significantly
improve the OFV.
So does it, after all, still make sense to include the BLOCK(2)?
Generally, at which step of model-building would you recommend to test for
parameter correlation?
Thanking you in advance,
Hauke
-----------------------------
Hauke Rühs
Apotheker
Pharmazeutisches Institut
- Klinische Pharmazie -
An der Immenburg 4
53121 Bonn
Tel: + 49-(0)228 73-5781
Fax: + 49-(0)228 73-9757
www.klinische-pharmazie.info