The 5 why’s can be used to investigate a specific failure to find a problems real root cause. If a problem is going to be fixed the real root cause needs to be understood.
The 5 Why’s tool enables you to probe deeper into cause and effect relationships, particularly when the team is generating x’s or causes at a symptom level. Identifying the root cause is more likely to cure the problem permanently. 5 Why is a simple but effective technique.
How does it work
Start with a priority* cause from the fishbone diagram and ask Why until there are no more actionable answers (often 3 is enough rather than 5) which will be closer to the root cause than the symptom you started with. Often a tree-like structure emerges as each question Why can yield more than one answer at any level. Often a good place to stop is when the cause is controlled by more than one level of management removed from the team.
*It is worth prioritising the causes from the fishbone otherwise a team can end up chasing root causes for relatively minor issues.
Once the real root cause is understood the chance of an effective solution is greatly increased.
Be careful not to let your answers get too broad – if you always end up concluding that the root cause is ‘poor management’ or ‘bad suppliers’ then it is not going to be specific enough.
Here’s what a completed basic 5 Why’s looks like:
Here’s a 5 Why that has different levels: