# Ceteris Lab downloadable Python script
# Course: Fundamentals of Python for Financial Econometrics

import numpy as np
rng=np.random.default_rng(31); T=20; donors=np.vstack([10+.2*np.arange(T)+rng.normal(0,.3,T) for _ in range(4)])
synth=donors.mean(axis=0); treated=synth+rng.normal(0,.15,T); treated[12:]+=2.5
print('average post-treatment gap', (treated[12:]-synth[12:]).mean())