The basic premise is

that you ask “why” 5 times and you will come to the root cause of a problem. Many times you can get to the root cause in less than 5 questions. I’m told that this is very similar to a method that was employed by Socrates, but, the Japanese have been around a lot longer than the Greeks, so I suspect that the Japanese learned it first.

Here’s an example that shows how it works: (and this just made up):

Q1. Why was the part defective?
A. Because the machine was not calibrated correctly.

Q2. Why was the machine was not calibrated correctly?
A. Because the regular maintenance was not performed.

Q3. Why wasn’t it performed?
A. Because Bob was out sick and he’s the only one who knows how to calibrate that machine.

Q4. Why is Bob the only one who knows how to calibrate the machine?
A. Because we never trained anybody else on that machine.
Q5. Why haven’t we trained anybody else?
A. Because we haven’t given Bob the time to train anybody else.

The conclusion: Provide time to train other employees and we can avoid defects like this in the future.

It is a great technique and often you can find more than one root cause. For example, question 4 could have been “why was Bob sick?” Asking the right questions takes practice.

Try it out. See if it works for you. Let me know if you have success!