Sample size for testing non-inferiority between two independent proportions

Note: The direction of the test is assumed depending on the ordering of the values for 'Difference' and 'Non-inferiority' margin. For 'Mean difference' < 'Non-inferiority margin', it is assumed that the aim is to show that the mean difference is indeed smaller than the non-inferiority margin. For 'Mean difference' > 'Non-inferiority margin', it is assumed that the aim is to show that the mean difference is indeed greater than the non-inferiority margin.

Probability in group 1

Probability in group 2

Difference in probabilities

Non-inferiority margin