Code to support post on significance levels required for two sample z test of proportions.

twosampleprobability2.py

def sample_required(p1, p_diff, alpha):
    if p_diff <= 0:
        raise ValueError("p_diff must be > 0")
    n = 1
    while True:
        z = z_calc(p1, p1+p_diff, n1=n, n2=n)
        p = 1 - stats.norm.cdf(z)
        if p < alpha:
            break
        n += 1
    return n