Prozanta Template
5 Why Analysis
Structured root cause analysis
Problem ID:
Owner:
Date:
How to use this template
5 Why is a simple root-cause method: you repeatedly ask “why?” until you reach the underlying system cause instead of stopping at the symptom. The method comes from the Toyota Production System, where Taiichi Ohno used it to get behind failures rather than just putting out fires.
When do you use it?
When a concrete problem has occurred and you want to stop it coming back — e.g. a recurring machine fault, a complaint or a delivery failure. Best for problems with a single chain of causes.
Time & participants
20-40 min with 2-5 people who know the process — not just management.
Step by step
- State the problem precisely — what, where, when and scale.
- Ask “why did it happen?” and write the answer down.
- Ask “why?” for each answer — typically five times.
- Stop when the cause is something you can change in the system — not “human error”.
- Define both a corrective and a preventive action with an owner and a deadline.
- Verify after implementation whether the problem has actually gone.
Watch out
- Don’t stop at “the employee made a mistake” — ask why the system allowed the mistake.
- Avoid guesswork — every answer must be verifiable with facts.
- One chain of causes at a time; if the problem branches, use a fishbone diagram.
Example
The line stood still for 40 min. → the motor overheated → lubrication failed → the lube pump was clogged → the filter wasn’t changed → there was no fixed maintenance plan. Root cause: missing preventive maintenance — not “the pump”.
Method: Taiichi Ohno, Toyota Production System (1978).
Read: Quality systems that work →Problem definition
What happened?
Where did it happen?
When did it happen?
The problem (precise statement — what, scale, effect)
5 Why Analysis
Why
1
Why did the problem occur?
Why
2
Why was that the case?
Why
3
Why was that so?
Why
4
Why was it possible?
Why
5
Why did the system allow it?
Root
Cause
The real, underlying cause
Solution / Action
Corrective action (now)
Preventive action (future)
Owner
Deadline
Verification
Expected result
Actual result (after implementation)
Verification date
Problem solved?
Prozanta · prozanta.dk
5 Why Analysis
Approved: