diff_diff.placebo_timing_test#
- diff_diff.placebo_timing_test(data, outcome, treatment, time, fake_treatment_period, post_periods=None, alpha=0.05, **estimator_kwargs)[source]
Test for pre-treatment effects by moving treatment timing earlier.
Creates a fake “post” indicator using pre-treatment data only, then estimates a DiD model. A significant effect suggests pre-existing differential trends.
- Parameters:
data (pd.DataFrame) – Panel data.
outcome (str) – Outcome variable column.
treatment (str) – Treatment indicator column.
time (str) – Time period column.
fake_treatment_period (any) – Period to use as fake treatment timing (should be a pre-treatment period).
post_periods (list, optional) – List of actual post-treatment periods. If None, infers from data.
alpha (float, default=0.05) – Significance level.
**estimator_kwargs – Arguments passed to DifferenceInDifferences.
- Returns:
Results of the fake timing placebo test.
- Return type: