I have my own spreadsheet I've used for many years and the sample size
calculation give n=16. However, my question is a little different: do
you really want to test the alternative that p=0? This seems
unrealistic in the real world. PASS will not accept p=0 as an
alternative. If I use p=0.00001, it gives n=14.
I would worry about the freeware a bit.
Tony
Peter A. Lachenbruch
Department of Public Health
Oregon State University
Corvallis, OR 97330
Phone: 541-737-3832
FAX: 541-737-4001
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Carlo Georges
Sent: Thursday, August 14, 2008 2:54 AM
To: [email protected]
Subject: st: Detection of disease
I tried to reproduce in stata the calculation needed for the following
case:
I need to determine the sample size, required to detct the presence of
disease in a population.
The formula is rather complex so it is difficult to paste in here,
For example i need to detect with 95% confidence the abscence of disease
in
a population where the presumed prevalence would be 20%. How lrge a
sample
size do I need to be 95% certain that the population is free from
disease.
I used a program "Winepiscope" freeware, that calculated a samplesize of
14.
in stata i tried : sampsi 0.2 0, power(0.9) onesample
and I get a result of :16
Can stata handle this type of calculation?
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