Comparative change overview — Difference-in-differences study

Question

State the intervention, target population and causal effect of interest.

Define intervention and comparison

Define adoption units, dates, comparison eligibility and potential spillovers or anticipation.

Align groups and periods

Align outcome periods and population definitions; distinguish panels from repeated cross-sectional samples.

Assess identification assumptions

Assess the plausibility of parallel untreated trends, no anticipation and stable measurement or composition.

Estimate effects

Choose an estimator for the adoption pattern, define aggregation and account for assignment-level dependence.

Assess sensitivity

Evaluate pre-intervention patterns, alternative controls, timing and sensitivity to assumption violations.

Report

Report group-specific patterns, estimates and uncertainty with explicit limits of the comparative counterfactual.

Comparative change overview

End flow

Protocol and decision register

Record the protocol, approvals and registration where applicable. Preserve planned decisions and amendments separately from results.

Protocol and rationale evidence

Attach the rationale and dated protocol, retaining amendments. A study registry records study details; a disease registry contains health data. The HMA–EMA Catalogue of RWD studies is one option for relevant studies. Check eligibility and applicable requirements, and record an identifier and timing if registered. Registration does not imply randomization.