# Re: distribution assumption of Eta in NONMEM

From: Ethan Wu <ethan.wu75>
Date: Fri, 28 May 2010 11:27:21 -0700 (PDT)

I could not find in the NONMEM help guide that explicitly mentioned a norma=
l distribution is assumed, only it was clearly mentioned of assumption of m=
ean of zero. ________________________________ From: Serge G=
uzy <GUZY
nm.com Sent: Fri, May 28, 2010 1:25:24 PM Subject: RE: [NMusers] distri=
bution assumption of Eta in NONMEM As far as I know, this is the as=
sumption in most of the population programs like NONMEM, SADAPT, PDX-MC-PEM=
and SAEM. Therefore when you simulate, random values from a normal distrib=
ution are generated. However, you have the flexibility to use any transform=
ation to create distributions for your model parameters that will depart fr=
om pure normality. For example, CL=theta(1)*exp(eta(1)) will  generate =
a log-normal distribution for the clearance although the random deviates ar=
e all from the normal distribution. I am not sure how you can simulate d=
ata sets if you are using the non parametric option that is indeed availabl=
e in NONMEM. Serge Guzy; Ph.D President, CEO, POP_PHARM www.poppharm.=
com         From:owner-nmusers
er-nmusers
10 9:08 AM To: nmusers
ssumption of Eta in NONMEM   Dear users,   Is it true NONMEM dose=
not assume Eta a normal distribution?   If it does not, I wonder wha=
t distribution it assumes? I guess this is critical when we do simulation=
s. Thanks     ________________________________ The informati=
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Received on Fri May 28 2010 - 14:27:21 EDT

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