Which statement about causal mechanism is true?

• A. Causation can be established without a causal mechanism.
• B. Evidence of a causal mechanism is required to establish causation.
• C. Correlation and causation are the same.
• D. A p-value guarantees causation.

Answer: (B)

Understanding causal mechanism means grasping how a cause leads to an effect through a concrete process. When we assess whether one thing causes another, having evidence about that process—how the change in the cause produces the outcome and through what steps—strengthens the causal claim. It helps show that the relationship isn’t just a coincidence or a byproduct of some other factor, and it clarifies why the effect would follow from the cause. In this view, demonstrating a plausible mechanism is part of establishing causation, not just observing that two things vary together.

The other ideas don’t fit as well. Causation isn’t proven by correlation alone, since two variables can move together without one causing the other. A p-value only tests probability under a null hypothesis and does not guarantee a causal link. And saying correlation and causation are the same is simply incorrect because causation implies a directional, causal relationship beyond mere association.