Which of the following is true about the relationship between correlation and causation?

• A. Correlation alone proves causation.
• B. Correlation alone proves causation.
• C. Causation is determined solely by chance.
• D. Causation requires evidence of a causal mechanism.

Answer: (D)

Correlation shows two things moving together, but it doesn’t explain why. Causation means one thing actually changes or produces a change in the other, and that requires more than just observing an association. Demonstrating a causal mechanism provides a plausible process by which one variable could bring about changes in the other, which helps distinguish a true causal effect from coincidences, confounding factors, or reverse causation. So, evidence of a causal mechanism strengthens the case for causation beyond what a mere correlation can offer. While not always known, a mechanism-based explanation is the strongest support among the options for claiming causation.