RE: sample size issue
Pete: CV (when not large) for a PK variable on the actual scale is
approximately the s.d. of the Log (PK), where Log (PK) can be assumed to
be normal. So one way to think it may be power the study in terms of
the sample standard deviation on the log-scale, referring a chi-square
test. Theoretically it might be doable. However, it is rare to see a
research hypothesis is framed in terms of s.d. and I have not seen a
study powered in terms of s.d..
- Bo
_____________________________________
BO JIN, Ph.D.
Clinical Pharmacology Statistics
Merck Research Labs
UG1D-44
PO Box 1000
351 North Sumneytown Pike
North Wales, PA 19454
Phone: 267-305-7876
Quoted reply history
________________________________
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
On Behalf Of Bonate, Peter
Sent: Wednesday, August 29, 2007 11:29 AM
To: [email protected]
Subject: [NMusers] sample size issue
Recently in an interaction with the FDA they asked us to power a
pharmacokinetic study to a given precision in a parameter estimate based
on a pop pk model in a population we have no experience with. In other
words, they wanted us to power a study to ensure that the standard error
of the population mean clearance was less than 30% CV. Does anyone know
how to do this a priori? Does this seem to be something new?
-
Thanks,
pete bonate
Peter L. Bonate, PhD, FCP
Genzyme Corporation
Senior Director, Pharmacokinetics
4545 Horizon Hill Blvd
San Antonio, TX 78229 USA
[EMAIL PROTECTED]
phone: 210-949-8662
fax: 210-949-8219
crackberry: 210-315-2713
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