One of the best books about it is "Chow, S.C.; Shao, J.; Wang, H. 2003. Sample Size Calculations in Clinical Research. Marcel Dekker. New York."
So your formula looks like:
n = (Zα/2+Zβ)2 * (p1(1-p1)+p2(1-p2)) / (p1-p2-NImargin)2
Zα/2=1.96
Zβ=0.84
better late than never
Andrei
Ready to join fellow brilliant minds for the SAS Hackathon?
Build your skills. Make connections. Enjoy creative freedom. Maybe change the world. Registration is now open through August 30th. Visit the SAS Hackathon homepage.