Two-Proportion z-Statistic

Problem

Return the two-proportion z-statistic (p1 - p2) / sqrt(p_pool*(1-p_pool)*(1/n1 + 1/n2)) with p_pool = (x1+x2)/(n1+n2). Return 0.0 when a sample size is not positive or the pooled proportion is 0 or 1.

Hint

The standard error always uses the pooled proportion under the null.

Test cases

case 1

in: [30,100,20,100]

expected: 1.6329931618554518

case 2

in: [50,100,50,100]

expected: 0

case 3

in: [10,50,5,50]

expected: 1.4002800840280096

case 4

in: [0,10,0,10]

expected: 0

case 5

in: [10,10,0,10]

expected: 4.47213595499958

Starter codePython

def two_proportion_z(x1, n1, x2, n2):
    # Your code here
    pass

5 test cases · run your code against them in the editor