Collider Bias Direction

Problem

Conditioning on a collider that is a common effect of treatment and outcome induces association between them. Return the sign of that induced bias as -1 * sign(treatment_to_collider) * sign(outcome_to_collider), where the inputs are the signed path coefficients. Return 0 when either path coefficient is zero.

Hint

Two positive arrows into the collider create a negative bias.

Test cases

case 1

in: [1,1]

expected: -1

case 2

in: [1,-1]

expected: 1

case 3

in: [-1,-1]

expected: -1

case 4

in: [0,1]

expected: 0

case 5

in: [2,3]

expected: -1

Starter codePython

def collider_bias_direction(treatment_to_collider, outcome_to_collider):
    # Your code here
    pass

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