Stata The Stata listserver
[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

st: Re: sample size calculation


From   Ricardo Ovaldia <ovaldia@yahoo.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: Re: sample size calculation
Date   Thu, 30 Sep 2004 10:03:43 -0700 (PDT)

Thank you to everyone that reply to my post. 
I also suspect, as Joseph pointed out, that the
statement in the article is incorrect regarding the
standard deviation.

Is it possible to compute a sample size if all you
know is the geometric mean and 95%CI.

Specifically if the geometric mean of a control group
is 2.52 (95% CI 2.28, 2.78) and I want to detect a
difference of say 0.5 between the GM of cases and
control, can this be done without additional
information?

Thank you again,
Ricardo. 

--- Joseph Coveney <jcoveney@bigplanet.com> wrote:

> From: Richard Williams wrote:
> 
> I think you meant
> 
> sampsi 100 110, alpha(0.025) power(0.8) sd1(15)
> sd2(15)
> 
> At least, that is what gives me an N of 43; the
> original command gives Ns
> of 20.
> 
> [Excerpted]
> 
>
----------------------------------------------------------------------------
> 
> Yep.  Either that or
> 
> -sampsi 100 110, alpha(0.0167) power(0.8) sd1(15)
> sd2(15)-,
> 
> which gives n = 48 for three tests between pairs of
> the three groups.
> 
> Sorry about that, and thanks to Richard for catching
> it.  (Talk about
> peppering with errors . . .)
> 
> Joseph Coveney
> 
> 
> 
> 
> 
> 
> *
> *   For searches and help try:
> *  
> http://www.stata.com/support/faqs/res/findit.html
> *   http://www.stata.com/support/statalist/faq
> *   http://www.ats.ucla.edu/stat/stata/
> 



		
_______________________________
Do you Yahoo!?
Declare Yourself - Register online to vote today!
http://vote.yahoo.com
*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/



© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index