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st: power calculations


From   louise hornstrup <louisehornstrup@hotmail.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: power calculations
Date   Thu, 4 Feb 2010 20:38:40 +0000

Dear listers,

I am doing two diffent studies, using Stata 11. The first is a cross-sectional study (n=42,298), the second a case-control study (n1=4,851/n2=4,851).

I am looking at a specific genotype with a frequency of 0.6% in both studies (variable of interest), the endpoint is IHD (Ischemic Heart Disease).  I have some difficulties with the power calculations. I want to estimate the minimal value (odds ratio) that can be detected with 80% power for both studies...But what is the right way to do this in Stata? As far as I can tell the sampsi command can+determine power or sample size - not minimal detectable effect size?


Best regards,


Louise Stig Hornstrup, MD, PhD-student
Dept. Clin. Biochem., 4111.
Rigshospitalet, Copenhagen
Denmark

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