Instructions: Enter parameters in the green cells. Answers will appear in the blue box below.
α (two-tailed) =
%
Threshold probability for rejecting the null hypothesis. Type I error rate.
β =
%
Probability of failing to reject the null hypothesis under the alternative hypothesis. Type II error rate.
P0 =
%
Proportion in Group 0 (baseline proportion)
N1
Number of participants in Group 1
N0
Number of participants in Group 0
P1 is expected to be
greater than
less than
the value of P0
Note that this calculator returns a slightly larger (less desirable) detectable effect size than some other calculators, because it adjusts for the Fleiss-Tytun-Ury continuity correction.


Follow this link to see the formula used in this calculator.


Reference:
Fleiss, JL, et al. Statistical methods for rates and proportions. Hoboken, NJ, J. Wiley; 2003. Page 79.