Re: st: RE: sample size calculation

[Richard Williams <Richard.A.Williams.5@nd.edu>]

At 12:31 PM 9/29/2004 -0700, Ricardo Ovaldia wrote:
> --- "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.
Actually, you do, don't you?  The original problem was

"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)"

So, for the SDs, you use 15.  But, I am not sure how you fill in the rest, 
especially since they came up with 3 groups, not 2.  Even if it was 2 
groups, I am not clear on how you would be expected to enter the means 
(take logs first or something?) In any event, I think the necessary 
information may be there, but I'm not sure either on what to do with it!

-------------------------------------------
Richard Williams, Notre Dame Dept of Sociology
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