Choose which calculation you desire, enter the relevant population values
(as decimal fractions)
for p0 (exposure in the controls) and RR (relative risk
of disease associated with exposure)
and, if calculating power,
a sample size (assumed the same for each sample).
You may also modify α (type I error rate) and the power, if relevant.
After making your entries, hit the calculate button at the bottom.
Reference: The calculations are the same as in
Comparing Proportions for Two Independent Samples
setting p1=p0 and p2= p0*RR/(1 + p0*(RR - 1)). See Schesselman, J. (1982),
Case Control Studies, p. 145