Sample Size Calculator for Comparing Two Proportions

Proportion in Each Group

Group 1 (e.g. 22 for 22%) ? Proportion in Group 1 Group 2 (e.g. 50 for 50%) ? Proportion in Group 2 Enrollment ratio ? Ratio of sample sizes (k)

Type I Error

Alpha (α) ? Type I error probability (%)

Type II Error

Beta (β) ? Type II error probability (%) Power (1 − β) ? Power of the test (%)