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Talichi Ohno, the creator of the 5-Why technique, is quoted using the following example to demonstrate using 5-Why’s for root cause analysis:

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.

What do you think? Is “NO FILTER ON THE PUMP” a root cause?

And if the inventor of 5-Why’s uses this as an example, should people call 5-Whys a root cause analysis technique?

Post your comments below.


Here are a couple more topics related to the 5-Whys and Root Cause Analysis that may be of interest to you:

What’s Fundamentally Wrong with the 5-Whys (Click here to read post.)

What’s Wrong With Cause-and-Effect, 5-Why’s, & Fault Trees (Click here to read post.)