converting epsilon to CV
From: "Williams, Gene, HMR/US" <Gene.Williams@hmrag.com>
Subject: converting epsilon to CV
Date: 16 Mar 1998 18:07:28 -0500
I notice that when epsilon enters a model as follows:
Y = F*(1 + EPS(1))
NONMEM output includes the following:
ERROR IN LOG Y IS MODELED
I have been using the SIGMA obtained using the above coding as an estimate of the CV of the residual variability as follows:
CV = SQRT(SIGMA)
However, if "ERROR IN LOG Y IS MODELED", shouldn't I be using:
CV = SQRT(e**SIGMA - 1)
I appreciate that for small values of SIGMA, these expressions are equivalent. However, for larger values of SIGMA, which equation is correct?
Thanks,
Gene
Gene Williams, Ph.D.
Clinical PK/PD
Hoechst Marion Roussel
Kansas City, MO, USA