{"id":"five-whys","model_id":"5 Whys","name":"5 Whys","summary":"5 Whys is a root-cause analysis method that repeatedly asks why a problem occurred. It continues past obvious symptoms until the underlying cause is reached, so countermeasures can prevent recurrence.","study_notes":["The specific number five is not the point; keep asking why until the root cause is reached and eliminated.","5 Whys is used with Gap from Standard problems, focusing on specific problem definition, goal setting, root cause analysis, countermeasure establishment, and checks, standards, and follow-up activities.","Root-cause analysis types listed are logic, one-variable-at-a-time (OVAT), and multivariate-at-a-time (MVAT).","Logic-based analysis such as 5 Whys requires no advanced math skills but requires critical thinking using inductive, deductive, and abductive logic.","Taiichi Ohno's example traces a machine stop from a blown fuse to an overload, insufficient lubrication, a lubrication pump issue, a worn pump shaft, and no strainer allowing metal scraps to enter.","Also called Five Whys."],"safety_notes":[],"sources":[{"url":"https://www.lean.org/lexicon-terms/5-whys/","title":"5 Whys - What is it? | Lean Enterprise Institute","accessed":"2026-10-25"}],"verification":{"status":"source_checked","checked_at":"2026-10-25","values":1,"method":"llm_source_check"},"updated_at":"2026-10-25","type":"operational","spec":{"kind":"methodology","related":[]},"url":"https://machineschema.com/operational/five-whys","license":"https://creativecommons.org/licenses/by/4.0/"}