Cronbach's Alpha

Problem

Return Cronbach's alpha (k/(k-1)) * (1 - sum(item variances)/total variance) for a list of items, where each item is a list of subject scores and variances are population variances. Return 0.0 when there are fewer than two items, lengths are inconsistent, or the total variance is zero.

Hint

Internal consistency grows with the average inter-item covariance.

Test cases

case 1

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

expected: 1

case 2

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

expected: 0

case 3

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

expected: 0.9142857142857144

case 4

in: [[[5,5],[5,5]]]

expected: 0

case 5

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

expected: 0

Starter codePython

def cronbach_alpha(items):
    # Your code here
    pass

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