The author of the 5-Why technique gives the following as an example of determining root cause:

1. “Why did the robot stop?” The circuit has overloaded, causing a fuse to blow.
2. “Why is the circuit overloaded?” There was insufficient lubrication on the bearings, so they locked up.
3. “Why was there insufficient lubrication on the bearings?” The oil pump on the robot is not circulating sufficient oil.
4. “Why is the pump not circulating sufficient oil?” The pump intake is clogged with metal shavings.
5. “Why is the intake clogged with metal shavings?” Because there is no filter on the pump.

People often struggle to complete this supposedly simple process. It only seems easy though, if you already know the answer before you start asking why.

As a typical example of how 5-Whys works, the “fifth why” is expected to uncover the root cause. Does “No filter on the pump” really represent a complete analysis or conclusive summary? Would you consider this a valid root cause?

What do you think of 5-Whys?

Let me know your thoughts below…