Which of the following is NOT a common root cause analysis method?

• A. 5 Whys
• B. Fishbone diagram
• C. Pareto chart
• D. Random guess method

Answer: (D)

Root cause analysis relies on structured, repeatable approaches that base conclusions on evidence and logic rather than chance. The random guess method fits no such structure—it’s not systematic, lacks documentation, and makes findings difficult to verify or repeat, which undermines the goal of preventing recurrence.

In contrast, 5 Whys guides you from the observed problem to its underlying causes by repeatedly asking why, a simple, practical way to drill down into processes or failures. The fishbone diagram (cause-and-effect diagram) visually groups potential contributing factors into categories like people, processes, equipment, materials, and environment, helping you see where problems may originate. The Pareto chart uses data to highlight the most significant causes, applying the 80/20 principle to prioritize improvement efforts.

So, the random guess method isn’t a credible tool for root cause analysis, while the others are standard, evidence-based techniques used to uncover and address underlying issues.