5 Whys

The 5 Whys is a question-asking technique used to explore the cause-and-effect relationships underlying a particular problem[1]. The primary goal of the technique is to determine the root cause of a defect or problem.

The vehicle will not start. (the problem)

  1. Why? - The battery is dead. (first why)
  2. Why? - The alternator is not functioning. (second why)
  3. Why? - The alternator belt has broken. (third why)
  4. Why? - The alternator belt was well beyond its useful service life and not replaced. (fourth why)
  5. Why? - The vehicle was not maintained according to the recommended service schedule. (fifth why, a root cause)
  6. Why? - Replacement parts are not available because of the extreme age of the vehicle. (sixth why, optional footnote)

Leave a Reply