Cohen's d

Problem

Return Cohen's d = (mean_x - mean_y) / sp with pooled standard deviation sp = sqrt(((n1-1)s1^2 + (n2-1)s2^2)/(n1+n2-2)). Return 0.0 when either sample has fewer than two values or the pooled variance is zero.

Hint

Standardized mean difference with a pooled within-group standard deviation.

Test cases

case 1

in: [[1,2,3,4,5],[2,4,6,8,10]]

expected: -1.2

case 2

in: [[1,2,3],[4,5,6]]

expected: -3

case 3

in: [[1,1,1],[2,2,2]]

expected: 0

case 4

in: [[10,12,14],[9,11,13]]

expected: 0.5

case 5

in: [[1],[2,3]]

expected: 0

Starter codePython

def cohens_d(x, y):
    # Your code here
    pass

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