Credible Interval Width

Problem

Compute the width of a symmetric credible interval from a posterior variance: 2 * z * sqrt(post_var), where z is the normal critical value.

Return 0.0 when post_var is not positive.

Hint

The width scales with the square root of the posterior variance.

case 1

in: [4,1.96]

expected: 7.84

case 2

in: [1,1.645]

expected: 3.29

case 3

in: [0,2]

expected: 0

case 4

in: [2.25,2]

expected: 6

Starter codePython

def credible_interval_width(post_var, z):
    # Your code here
    pass

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