designing-experiments

# Designing Experiments Helps select the appropriate causal inference method. ## Decision Framework 1. **Control Group?** * **Yes**: Go to Step 2. * **No**: Consider **Interrupted Time Series (ITS)**. 2. **Unit Structure?** * **Single Treated Unit**: * With multiple controls: **Synthetic Control (SC)**. * No controls: **ITS**. * **Multiple Treated Units**: * With control group: **Difference-in-Differences (DiD)**. 3. **Time Structure?** * **Panel Data** (Multiple units over time): Required for DiD and SC. * **Time Series** (Single unit over time): Required for ITS. ## Method Quick Reference * **Difference-in-Differences (DiD)**: Compares trend changes between treated and control groups. Assumes **Parallel Trends**. * **Interrupted Time Series (ITS)**: Analyzes trend/level change for a single unit after intervention. Assumes **Trend Continuity**. * **Synthetic Control (SC)**: Constructs a synthetic counterfactual from weighted control units. Assumes **Convex Hull** (treated unit within range of controls).