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Getting the Most Out of the 5 Whys

by Emmanuel Jallas
November 6, 2013

Getting the Most Out of the 5 Whys

by Emmanuel Jallas
November 6, 2013 | Comments (7)

The 5 whys is one of the most well-known and popular lean tools, and it’s also one of the trickiest. 

If we aren’t careful, it can end in a vicious circle, a continuous loop of why’s and because’s answering each other. Instead of getting us to the root cause, it can just end up feeling like a dead end.

In a recent workshop, I was explaining how to use the 5 whys effectively. We discussed a real life situation a particular company was facing, in which the customer received the wrong product model. In our trail to the root cause we were quickly stopped by the statement, “The warehouseman didn’t apply the standard.” This wasn’t a suitable answer though, because apart from the occasional saboteur, which wasn’t the case here, people don’t commit mistakes deliberately. TPS thinking tells us, “If the problem happened, this is only because it could.” In other words, if someone turned right instead of left, this is only because this person could (you have to prevent the person from being able to turn right).

Maybe your 5 whys process recreates this same vicious circle, focusing on one faulty worker. The first of the 4 M’s, Manpower, is often the scapegoat of our attempts at root cause analysis. So, what do we do? Do we discard the 5 whys methodology, as it brings us to dead ends or to blaming people most of the time?

The most known 5 whys example is Taiichi Ohno’s. Notice that this example doesn’t end in a vicious circle, like this: Why doesn’t the pump circulate enough oil? Because there isn’t enough in oil pan. Why isn’t there enough oil in oil pan? Because the pump is not circulating enough oil, and oil return is poor. Nor does it end in blaming people, like this: Why doesn’t the pump circulate enough oil? Because the operator didn’t put enough oil, and didn’t pay attention to oil level and pressure.

Remember in our scenario, we had initially arrived at a dead end, too: “The warehouseman didn’t apply the standard. We have to explain him why this standard is important, and how to apply it.”

So what are Taiichi Ohno’s secrets to drive the 5 whys more rigorously than us, eventually leading to the real root cause?

Here are two tips for how to avoid a dead end situation:

A) If you get into a vicious circle between why and because, or you end up with something like, “We must raise people’s awareness about standards,” you aren’t at the root cause. Simply start over, try again, and consider new points of view.

B) Go to the gemba and follow the footsteps of the person closest to the work. Follow the standard process for doing the work and ask other problem solving group members to watch you carefully. You’ll quickly see where the standard fails. This is no more than the TPS principle of “Go see… again!” but instead of focusing on manpower, you’re focusing on the other 3Ms: Material, Methods, and Machines.

So what happened with our real life scenario with our warehouseman? In the end, we discovered that the products weren’t identified singly, only their location was labeled. This could not possibly prevent mix ups. So the correct countermeasure wasn’t to teach the warehouseman how to do his job again, but to provide him with a device with which to identify each product upon arrival in the warehouse. This process fix became the new standard and the problem was solved, but after very carefully applying the 5 whys process.

What are your tips for making sure the 5 whys works for you?

The views expressed in this post do not necessarily represent the views or policies of The Lean Enterprise Institute.
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Bob Wallner November 06, 2013
13 People AGREE with this comment

5 Why is one of my favorite tools both to use and to teach.  Simple yet powerful.

The way I learned the 5-Why's is that it is a downward staircase where each stair you go down needs to be answered by an appropriate "WHY"; however, to ensure it is a logical statement, you also need to be able to “walk up” the stairs.  

To do this you must be able to reverse the question to a statement using "Therefore".  If the "WHY" & the "Therefore" don't both work you don't have an accurate Cause.  

I overslept today...Why? My alarm didn't go off (Down Stairs) - my alarm didn't go off...therefore I over slept today (Up Stairs) – it works as a direct cause

I overslept today…Why? Batteries were dead in clock (Down Stairs) – The batteries were dead in clock…therefore I over slept today (Up Stairs) – doesn’t directly work.  Did you skip a couple Whys?


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Emmanuel JALLAS November 06, 2013
Thank you for your comment Bob. You're right to stress the need to always run the "therefore" test, and your example is very pedagogic. Thank you for sharing.

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Diana Claros November 07, 2013
3 People AGREE with this comment
I think it is very important that your 'final' cause: a) don't blame anybody else for the problem under analysis, b) is something controllable, and c) doesn't end in something like more training or more resources. It is true that training is something really good and important, but if you train people to do the same process that is producing the problem you are analyzing, this is not going to solve the problem. It will only reproduce the poor results. That's why the 5 whys is such a powerful tool: because it questions your traditional assumptions and the way you normally do something. Gemba, as you mentioned, is a good companion for 5 whys.

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Emmanuel Jallas November 11, 2013

Thank you Diana for your comment.

I didn't knew it while writing this Lean Post, but found it later : Art Smalley is stressing your point in this Lean Edge Post (http://theleanedge.org/?p=255308#!)

"Be suspicious of any thinking process that primarily ends up with re-drafting standardized work, re-training employees, as the solution space. Normally it is missing the more fundamental cause or problematic area…That is a continual problem I see with Lean programs."

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Marty November 15, 2013
If my whys end up with "a person did something incorrectly", I ask why again.  There's always an underlying reason why people are able to make mistakes.  I agree that going to the Gemba is the best way to answer why and get to real cause. 

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Yvonne November 19, 2013
EXCELLENT  Article and example. Thanks!

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Mohamed Adel June 03, 2021

thanks for this excellent article but the human error is existing and can't be avoided specially if the process is a standard process and the worker is doing it long time ago so the worker may keep in mind that he/she kept the standard in mind and so the human error may appear. 

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