In cascade or stepwise modeling, what sequence is tested?

• A. Intervention → Outcome → Mediator
• B. Intervention → Mediator → Outcome
• C. Outcome → Mediator → Intervention
• D. Moderator → Mediator → Outcome

Answer: (B)

In cascade or stepwise modeling, the idea is to test a mediation pathway where the intervention influences the mediator, and the mediator then influences the outcome. The sequence runs Intervention → Mediator → Outcome because the mediator is the mechanism through which the intervention affects the outcome. You’d typically check that the intervention predicts the mediator, the mediator predicts the outcome while controlling for the intervention, and that the direct effect of the intervention on the outcome shrinks when the mediator is included. This ordering captures how the change is transmitted through the mediator to produce the outcome. If you tried Outcome first, it would imply the mediator comes after the outcome, which doesn’t test the causal chain. If you started with a Moderator, that would be testing a different kind of effect (an interaction) rather than a chained process through a mediator.