NONMEM Users Network Archive

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Re: FW: advan8 vs. advan13 (CORRECTION)

From: Nick Holford <n.holford>
Date: Thu, 05 Nov 2009 16:40:05 +1300

Peiming,

Thank you for pointing out my mistake again!

Perhaps next time you should make the correction and send it to nmusers :-)

MU_1=LOG(THETA(1)/(1-THETA(1)) ; logit of population bioavailability

EXPP=MU_1+ETA(1) ; add random effect

BIO=1/(1+EXP(-EXPP)) ; individual bioavailability



Nick

Ma, Peiming wrote:
>
> Unfortunately, Nick, you have an extra EXP: the denominator of BIO
> should be just 1 + EXP(-EXPP). J
>
>
>
> Cheers,
>
>
>
> ------------------------------------------------------------------------
>
> *From:* owner-nmusers
> [mailto:owner-nmusers
> *Sent:* Wednesday, November 04, 2009 3:43 PM
> *To:* nmusers
> *Subject:* Re: [NMusers] advan8 vs. advan13 (CORRECTION)
>
>
>
> Hi,
>
> Thanks to Peiming Ma and Thuy Vu for pointing out an error in my
> attempt to transform bioavailability into its logit.
>
> The logit transformation of a probability is ln(P/(1-P)) i.e. the log
> of the odds ratio. The reverse transform is correct i.e. exp(logit) is
> the odds ratio and P is then OR/(1+OR) (or 1/1+exp(-logit)).
>
> If THETA(1) is the bioavailability then this is (I hope) the correct
> transformation of THETA(1) and reverse transform to get the
> individual bioavailability with a random effect constrained to be
> within 0 and 1.
>
> MU_1=LOG(THETA(1)/(1-THETA(1)) ; logit of population bioavailability
>
> EXPP=MU_1+ETA(1) ; add random effect
>
> BIO=1/(1+EXP(-EXP(EXPP))) ; individual bioavailability
>
>
> Nick
>
> --
> Nick Holford, Professor Clinical Pharmacology
> Dept Pharmacology & Clinical Pharmacology
> University of Auckland,85 Park Rd,Private Bag 92019,Auckland,New Zealand
> tel:+64(9)923-6730 fax:+64(9)373-7090 mobile:+64(21)46 23 53
> email: n.holford
> http://www.fmhs.auckland.ac.nz/sms/pharmacology/holford

--
Nick Holford, Professor Clinical Pharmacology
Dept Pharmacology & Clinical Pharmacology
University of Auckland,85 Park Rd,Private Bag 92019,Auckland,New Zealand
tel:+64(9)923-6730 fax:+64(9)373-7090 mobile:+64(21)46 23 53
email: n.holford
http://www.fmhs.auckland.ac.nz/sms/pharmacology/holford


Received on Wed Nov 04 2009 - 22:40:05 EST

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