 Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at statalist.org.

# re: st: sampsi and percentages

 From "Ariel Linden, DrPH" To 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

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/
```