5 Whys
Updated 2026-08-08
INTRODUCTION
English translation pending.
CORE DEFINITION
The five whys technique, associated with Sakichi Toyoda and used within the Toyota production system, asks why a problem occurred and then why again, continuing for at least five rounds until the answer reaches a cause that can be acted on. The count is a guideline rather than a rule, and the process stops when further questioning reaches a systemic cause rather than another symptom. Acting on the root cause prevents recurrence instead of treating the visible failure.
SCAFFOLDING EFFECT
Reduce cognitive load
- Ask again: treat each answer as a symptom until you reach a cause you can change. - Keep it about systems: direct the questions at the process rather than at a person. - Stop at actionable: end when the cause is something the organization actually controls.
Anchor fast decisions
A visible failure is usually the last link in a chain of conditions, and fixing it removes the symptom while leaving the chain intact. Each successive why moves one link upstream toward the conditions that produced the failure. The process stops where a change is possible, since causes beyond the organization's control cannot be acted on.
MINIMUM ACTION
In progress 0/1Practice this model in one real situation:
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Source support: Explicit
- en.wikipedia.orghttps://en.wikipedia.org/wiki/Five_whysverified
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