Parallel Trends Check

Problem

Check the parallel trends assumption: compute the treated-minus-control difference in each pre period and return True when every difference is within tolerance of their mean.

Empty input returns True.

Hint

A stable pre-period gap supports the difference-in-differences design.

Test cases

case 1

in: [[10,12,14],[8,10,12],0.1]

expected: true

case 2

in: [[10,12,14],[8,10,11],0.5]

expected: false

case 3

in: [[],[],0.1]

expected: true

Starter codePython

def parallel_trends_check(treat_pre, control_pre, tolerance):
    # Your code here
    pass

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