5-Whys Example – Is this Root Cause Analysis? (Updated)
Most Famous Example of 5-Whys
Taiichi Ohno (pictured above), created the 5-Why technique. He is quoted using the following 5-Why example to teach the technique:
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.
This is the inventor of the technique and his most famous 5-Why example. If the inventor of 5-Whys uses this 5-Why example, certainly this is a “good” example of how 5-Whys works. And “No Filter” is his root cause (the fifth why).
Is “No Filter” a Root Cause?
I would never call “NO FILTER ON THE PUMP” a root cause. Would you?
This 5-Why example isn’t abnormal. It is typical of many of the 5-Why examples I have seen people struggle to complete. (Examples HERE)
Struggle? Isn’t 5-Whys suppose to be easy?
It is easy … But it is ONLY easy if you already know the answer BEFORE you start asking why.
I had a relative who works in a factory. The boss was taught 5-Whys. When something goes wrong, he starts asking. “Why.” The worker says that if they knew “Why” they would fix it or they would not have the problem to start with. So, they make up answers to his why questions because they know he won’t stop asking why until he gets to five. They try to think of answers where no one will be blamed. The worker says they usually figure that they will just be more careful.
What do you think of 5-Whys? Let me know your thoughts below…
And that brings us to several limitations or drawbacks of using 5-Whys…
5-Why Drawback 1: Confirmation Bias
What is “Confirmation Bias?”
The term was developed by researchers to highlight a problem with the scientific method. When someone thinks they “know” the answer, they preferentially look for evidence that confirms their answer. Thus, they have a confirmation bias.
Because 5-Whys is easy when you “know” the answer … 5-Whys frequently suffers from confirmation bias (the investigator naturally looks for evidence that makes their 5-Why chain work and ignores evidence that is counter to their beliefs). Frankly, if you know the answer, why look for evidence at all!
Thus when asking why, the investigator finds the answer they started out to prove.
For more reading about Confirmation Bias, see:
5-Why Drawback 2: Focus on a Single Root Cause
If you follow a single 5-Why questioning chain you only get one root cause. Just like Taiichi Ohno did.
But is there just one root cause for the robot example?
In another analysis of this example using the TapRooT® System, we found four Causal Factors. Each Causal Factor has at least one root cause and maybe more. That means that Taiichi Ohno missed at least three root causes. To see the comparison of Taiichi’s example and the TapRooT® Analysis, go to:
Failure to consider multiple root causes is a common problem when using 5-Whys. Have a look at the example in this professional society magazine (the bugs example – click on the cover below).
5-Why Drawback 3: No Guidance to Find the Causes of Human Errors
5-Whys often stops at “human error” as a root cause. But as we explained in this article:
Human error is NOT a root cause.
Most people investigating problems have no training in human factors (the science of human error). That’s why we included human error analysis guidance in the TapRooT® System. You can see how some of the embedded intelligence in the TapRooT® System works if you read the article referenced above.
Are You Dissatisfied with 5-Why Root Cause Analysis?
We don’t find that surprising that you find 5-Whys lacking. The three drawbacks listed above are just some of the reasons why 5-Why analysis is usually insufficient to find root causes. Even smart, well-trained users (Like Taiichi, himself) frequently jump to conclusions, follow a single root cause trail, and fail to adequately analyze the causes of human error. That’s why 5-Why examples like the one above (the robot example) aren’t rare.
Perhaps it is time you discovered the fundamentals of root cause analysis and learned an advanced root cause analysis system – TapRooT®!
Learn More About TapRooT® Advanced Root Cause Analysis
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