Re: st: question on calculating power from incidence rates

[Steven Samuels <sjhsamuels@earthlink.net>]

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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