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A two-period design subtracts levels instead of changes · case 04

A two-period design subtracts levels instead of changes.

Member previewVariant 4 · 3 implementations · 6 checks per implementation

Case contract

Input [treated_pre,treated_post,control_pre,control_post] defines a synthetic two-period contrast. Return (treated_post-treated_pre)-(control_post-control_pre); this arithmetic alone does not assert parallel trends.

Why this case matters

A deterministic synthetic study model isolates this data-contract defect; outputs alone establish no real-world causal identification.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
baseline imbalance	`40`	`8`	Failed

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