5 Whys method
The 5 Whys is a simple technique: state the problem, then ask "why did that happen?" until you reach a cause you can fix. Five is a guide, not a rule. Sometimes three is enough, sometimes more.
How to do it
- Write the problem as one clear sentence.
- Ask why it happened, and answer with a fact you can check.
- Ask why again about that answer.
- Stop when you reach a cause the organisation can control and fix.
- Turn that cause into actions with owners and dates.
Worked example: conveyor drive motor trips
| Problem | The conveyor drive motor tripped on overload twice this week. |
|---|---|
| Why 1 | The motor drew too much current because the gearbox was stiff. |
| Why 2 | The gearbox bearing ran hot and dry. |
| Why 3 | The auto-lubricator reservoir was empty. |
| Why 4 | Nobody refilled it. |
| Why 5 (root cause) | Lubricator refill is not a task on the preventive maintenance checklist. |
Actions: replace the bearing (corrective); add a lubricator check and refill to the monthly PM, and fit level indicators (preventive).
Tips
- Use facts. "Probably the operator" is a guess, not a Why.
- Do not stop at a person. Ask why the procedure allowed it.
- Branch when needed. One problem can have more than one cause chain. A fishbone diagram helps.
- Check the chain backwards. Read from the root cause up with "therefore". It should make sense.
RapidRCA builds the Whys for you, and you can edit any of them.
Try it on a real failure.
Describe what happened or photograph your notes, and RapidRCA builds the analysis with the ROOTS™ method.
Start an RCA
Describe what happened or photograph your notes, and RapidRCA builds the analysis with the ROOTS™ method.
Start an RCA