Run Sensitivity Analysis

Pre-specify a small set of defensible perturbations:

• alternative comparable pre-period windows;
• exclusion of a substantively suspect or dominant donor;
• plausible cooldown or measurement-start choices;
• DGP rank and effect-pattern choices for power;
• outcome definitions fixed before post-period inspection;
• eligible geography aggregations justified by media delivery and spillover.

For each run, save its panel hash, config, artefacts, and rationale. Compare ATT, intervals, p-values, pre-fit, donor weights, placebo support, MDE, and failure rates. Distinguish robustness to a design choice from fishing over arbitrary specifications.

If the decision changes under small, equally defensible perturbations, report the result as specification-sensitive. Do not average incompatible estimands.