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re: st: sampsi and percentages


From   "Ariel Linden, DrPH" <ariel.linden@gmail.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   re: st: sampsi and percentages
Date   Tue, 30 Aug 2011 08:51:05 -0400

Ricardo,

I may be mistaken here, but it seems you have two proportions (if it's
bounded between 0,1 then you have a numerator and a denominator for each
group).

If that is truly the case, you can use sampsi for proportions:

. sampsi 0.25 0.4

Estimated sample size for two-sample comparison of proportions

Test Ho: p1 = p2, where p1 is the proportion in population 1
                    and p2 is the proportion in population 2
Assumptions:

         alpha =   0.0500  (two-sided)
         power =   0.9000
            p1 =   0.2500
            p2 =   0.4000
         n2/n1 =   1.00

Estimated required sample sizes:

            n1 =      216
            n2 =      216

I hope this helps

Ariel

Date: Mon, 29 Aug 2011 11:40:33 -0700 (PDT)
From: Ricardo Ovaldia <ovaldia@yahoo.com>
Subject: st: sampsi and percentages

 
 
I need to compute sample size and power for a study comparing two group on a
measurement bounded by (0,1), (a measure of intensity).
I was thinking about using -sampsi- to power on the difference of means.
However, this seems strange to me, is there another way to power such
comparison?
 
Thank you,
Ricardo

Ricardo Ovaldia, MS
Statistician 
Oklahoma City, OK



	

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