[R-sig-ME] Stats question

Ken Beath kjbeath at kagi.com
Thu Jul 31 10:03:31 CEST 2008

On 31/07/2008, at 2:46 PM, Iasonas Lamprianou wrote:

> Dear friends,
> I am not sure that this is the right place to ask,  but please feel  
> free to suggest an alternative discussion group.
> My question is that I want to do a comparative study in order to  
> compare the rate of incidence in two populations. I know that a  
> pilot study was conducted a few weeks ago and found 8/140 (around  
> 6%) incidence in population A. Population B was not sampled.  
> Assuming this is (about) the right proportion in the Population A  
> what is the sample size I need for population A and B in the main  
> study, in order to have power of 80% to idenitfy significant  
> differences? I would expect the incidence in population B to be  
> around 10% compared to the 6% of the Population A.
> Any suggestions?

This isn't really the appropriate e-mail list, but samplesize.bin in  
Hmisc should be what you need, note that it returns the total sample  
size.  It is also useful to read the chapter on sample size from a  
clinical trials book.


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