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Re: st: question on calculating power from incidence rates


From   Steven Samuels <sjhsamuels@earthlink.net>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: question on calculating power from incidence rates
Date   Thu, 17 Apr 2008 10:50:31 -0400

Dear Maren:

With only this information it is not possible to estimate power. Under the simplest assumption--constant group hazard rates, no confounding factors-you would also need the person-years in each group.

-Steven

On Apr 17, 2008, at 8:34 AM, Maren Weischer wrote:


Dear Statalisters



I have a question on calculating power from incidence rates per 100.000
person years.

Is it possible? I only have this information for two groups: incidence
rates of breast cancer of 27.2 and 25.5 / 100.000 years and a p value
from a fishers exact test p=.84.

I want to determine the relative risk of breast cancer that I have 80%
power to detect?



Kind regards



Maren Weischer,

Dept of Clinical Biochemistry,

Herlev University Hospital.

Denmark


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