What is the 5 Whys?
The 5 Whys, developed by Sakichi Toyoda and used across Toyota, is a root-cause technique: state the problem, ask why it happened, then ask why again for each answer. Five is a guide, not a rule — stop when you reach a cause that, if fixed, would stop the problem recurring.
5 Whys example: a customer received the wrong order
- Why? — The packer picked the wrong item.
- Why? — Two products have almost identical labels.
- Why? — The new supplier's packaging wasn't checked when we switched.
- Why? — There's no step to review packaging when a supplier changes.
- Why? — Supplier changes are handled only by purchase, without operations sign-off.
- Root cause → add an operations check to every supplier change.
Tips for a good 5 Whys
- Do it with the people closest to the problem.
- Base each answer on facts, not guesses.
- Focus on processes, not on blaming people.
- For complex problems with several causes, use a fishbone diagram alongside.
How DOOfy helps
The 5 Whys works best with facts at hand. AIMOS One links orders, stock, suppliers and people data, so each “why” can be answered with records rather than memory — and NIMMI can help pull those records together.
Frequently asked questions
Do you always need to ask “why” five times?
No. Stop when you reach a cause that you can act on and that would prevent the problem from recurring — it may take three whys or seven.
What is the limitation of the 5 Whys?
It follows one chain of cause and effect, so it can miss problems with several contributing causes. A fishbone (Ishikawa) diagram helps in those cases.