|Find sample size:
If you know the two proportions, use this side to find how many subjects you need.
|Find effect size:
If you know the proportion and number of subjects for Group 1, use this side to find detectable proportions for Group 2.
The calculations here use equations 4.18 & 4.19 in J.L. Fleiss, et al.,
Statistical Methods for Rates and Proportions, 4th ed., and are consistent with their Table A.4. The results here may differ from other webpages or software because most of them ignore the
continuity correction. The Fleiss book discusses the importance of the continuity correction;
see also Levin and Chen, American Statistician 53:62-66.
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