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Re: st: RE: sample size calculation


From   Ricardo Ovaldia <ovaldia@yahoo.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: sample size calculation
Date   Wed, 29 Sep 2004 12:31:59 -0700 (PDT)

--- "Lin, Chung-Tung" <Chung-Tung.Lin@cfsan.fda.gov>
wrote:

> you may want to look at the sampsi command for
> details.

Thank you Jordan Lin, but -sampsi- requires that you
specify means and SD, which I do not have and is the
reason that I asked the question.

Regards,
Ricardo.

> 
> 
> -----Original Message-----
> From: Ricardo Ovaldia [mailto:ovaldia@yahoo.com] 
> Sent: Wednesday, September 29, 2004 2:04 PM
> To: statalist@hsphsun2.harvard.edu
> Subject: st: sample size calculation
> 
> 
> Dear all,
> 
> In an article that I am reading the authors write:
> 
> "it was decided a priori to include a minimum
> quantity
> of mother, which could allow the statistical power
> (alpha=0.05, beta=0.80) for assessing
> differences of 10% in nicotine concentration by
> group
> with an expected standard deviation of 15 ng/mg.
> These
> criteria led to the analysis of 150 mothers (50 for
> each of the 3 groups)" 
> 
> They claim that they did this and all analysis using
> Stata 5.0. They do not provide group means or any
> descriptive statistics on which the sample size was
> computed.
> 
> Can someone please tell me how this could have been
> done. And is there a program to do this in Stata?
> 
> Thank you in advance,
> Ricardo
> 
> 
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=====
Ricardo Ovaldia, MS
Statistician 
Oklahoma City, OK


		
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