In the Five-Why Method, which question best ensures the root cause is described in measurable terms?

• A. Why would this approach reduce costs?
• B. Why do we need to collect data to support the root cause?
• C. Why should we monitor results after implementing?
• D. Why, in measurable terms, are the preventive strategies or newly developed solutions operable or inoperable?

Answer: (D)

When using the Five-Why method, you want the final corrective actions to be testable and trackable. The best option pushes you to describe the root cause’s remedy in measurable terms by asking whether the preventive strategies or new solutions are operable or inoperable, and to do so with concrete, observable criteria. This means defining exactly how you’ll know the solution works (or doesn’t), under what conditions, and with what metrics or thresholds. It turns the remedy into something you can measure, test, and sustain, rather than just describe in vague terms.

Other prompts focus more on potential effects or post-implementation checks. Asking about cost reductions concerns impact rather than how to verify feasibility in measurable terms. Asking to collect data to support the root cause is about gathering evidence for the cause itself, not about whether the proposed fix can be executed and sustained. Asking to monitor results after implementing is important for follow-up, but it doesn’t require framing the remedy in measurable, operable terms from the start.