[R] stats question

From: Iasonas Lamprianou <lamprianou_at_yahoo.com>
Date: Wed, 30 Jul 2008 21:46:42 -0700 (PDT)


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? How can I do this in R?  
Jason



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