Correlation vs. Causation

Correlation means two things move together (e.g., when ad spend goes up, sales go up), but one doesn’t necessarily cause the other. Causation means one variable directly influences another (e.g., running an ad causes incremental sales). Umbrella analogy: More umbrellas and more rain are correlated, but rain causes umbrellas — not the other way around. ‍ Understanding this difference is essential when interpreting MMM results, which infer causality statistically rather than experimentally.