(Photo: Ad Meskens)
If you’ve ever had training on root cause analysis (RCA) you will almost certainly have learnt about Five Whys. Keep asking ‘why’ five times until you get to the root cause. The most famous example is of the Lincoln Memorial in Washington. The summary of this Five Whys example is reproduced below from an article by Joel A Gross:
Problem: The Lincoln Memorial in Washington D.C. is deteriorating.
Why #1 – Why is the monument deteriorating? Because harsh chemicals are frequently used to clean the monument.
Why #2 – Why are harsh chemicals needed? To clean off the large number of bird droppings on the monument.
Why #3 – Why are there a large number of bird droppings on the monument? Because the large population of spiders in and around the monument are a food source to the local birds
Why #4 – Why is there a large population of spiders in and around the monument? Because vast swarms of insects, on which the spiders feed, are drawn to the monument at dusk.
Why #5 – Why are swarms of insects drawn to the monument at dusk? Because the lighting of the monument in the evening attracts the local insects.
Solution: Change how the monument is illuminated in the evening to prevent attraction of swarming insects
This example is easy to understand and seems to demonstrate the benefit of the approach of Five Whys. Five Whys is simple but suffers from at least two significant flaws – i) it is not repeatable and ii) it does not use all available information.
Different people will answer the why questions differently and their responses will take them to a different conclusion. For example to Why #2 “Why are harsh chemicals needed?”, the response might be “Because the bird droppings are difficult to remove with just soap and water”. This leads to Why #3 of “Why are bird droppings difficult to remove with just soap and water?” and you can see that the conclusion (“root cause”) will end up being very different. The approach is very dependent on the individuals involved and is not repeatable.
Other questions that would be really beneficial to ask but would not be asked using a Five Why approach are:
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- When did the problem start? Armed with the answer to this might have helped link the timing with when the lighting timing was changed.
- How many other monuments have this problem? If other monuments do not have this problem then what is different? If other monuments have this problem then what is the same? This line of questioning is, again, more likely to get to the lighting timing quickly and reliably because a monument without lighting and without the problem suggests the lighting might have something to do with the cause.
In my last post I described a hypothetical situation of a vaccine trial where subjects had received expired vaccine. If we use the Five Whys approach, it might go something like:
Why did subjects receive expired vaccine? Because an expired batch was administered at several sites; Why was an expired batch administered at several sites? Because the pharmacists didn’t check the expiry date; Why didn’t the pharmacists check the expiry date? Here we get stuck because we don’t know. So maybe we could try again.
Why did subjects receive expired vaccine? Because an expired batch was administered at several sites; Why was an expired batch administered at several sites? Because the expired batch wasn’t quarantined. Why wasn’t the expired batch quarantined? Because sites didn’t carry out their regular check for expired vaccine. Why didn’t sites carry out their regular check for expired vaccine? Because they forget maybe? Or perhaps didn’t have a system in place? As I hope you can see, we really end up in guess work using Five Whys because we are not using all the available information. Information such as which sites had the problem and which didn’t? When did the problems occur? What is the process that ensures expired vaccine is not administered? How did that process fail?
Five Whys can be fitted to the problem once the cause is known but it is not a reliable method on its own to get to root cause. Why is definitely an important question in RCA. But it’s not the only question. To quote the author of ‘The Art of Problem Solving’, Edward Hodnett, “If you don’t ask the right questions, you don’t get the right answers. A question asked in the right way often points to its own answer. Asking questions is the ABC of diagnosis. Only the inquiring mind solves problems.”
Here are more of my blog posts on root cause analysis where I describe a better approach than Five Whys. Got questions or comments? Interested in training options? Contact me.
Note: it is worth reading Gross’s article as it reveals the truth behind this well-known scenario of Lincoln’s Memorial.
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This is why Lean Six Sigma seeks to validate the answer to “Why” with hypothesis tesying of the data. If you don’t know for certain the root cause, you need the Six Sigma side of things.
I agree that “the 5 whys” is just part of the problem solving approach. I’ve written about it here in these posts:
http://www.leanblog.org/2015/11/you-just-have-to-ask-why-five-times-lean-or-leanstartup-requires-more-than-that/
http://www.leanblog.org/2015/11/maybe-we-should-call-it-the-many-whys-instead-of-the-five-whys/
I agree with the author’s statements regarding 5-whys. However, since I work in the automotive industry, it is a common request from OEM’s to complete a 5-why. Utilizing my Six Sigma training, I try to define a problem statement answering the questions below.
What?
Where?
When?
How much?
Answering these questions, usually scopes a problem fairly well.
I agree with all the comments from the point of being just one tool in the suite of LSS tools to use as you walk through the DMAIC process. Like in the story about the Lincoln Memorial, my thought always come back to the Control phase. The story is missing that element. To me the 5 Why’s get you somewhere just like a really busy fishbone diagram, but in the control phase you can monitor the results of the other efforts to see if rest of the process was fruitful.
I am somewhat of a traditionalist with regard to the
use of the “5-Whys” method of cause investigation
(notice that I used the term investigation vs. analysis).
I will come back to discuss that distinction a bit later.
First, I refer to traditional as way of referring to the
classic use of 5-whys to identify the “root cause”. In
this context I think of it as the most basic, simple and
practical way to identify the root cause that I know of.
To arrive at this rationale one needs to apply a few basic
assumptions, such as:
1. that the problem situation is empirical (in other
words the situation can be observed)
2. that the situation is understood well enough to be
able to “locate the point of cause” — use: “4 W’s & H”
(the “PoC” is the point where the “direct cause” can be
observed)
3. that it is understood that there is nothing sacred
about the number ‘5’ in “5-Whys Cause Investigation”
and that you ask as many whys as necessary to
identify the root cause.
In my view, once these assumptions are accepted, it becomes fairly straight-forward to practically apply the use of the 5-why method effectively.
My experience suggests that most of us come-by our thinking about subjects such as this through what we learned and did at the different companies where we have worked. This certainly applies in my case. In fact, the company where I learned to use “5-Why Cause investigation” had a method of doing problem solving in empirical situations. It was called “Practical Problem
Solving” based on a CA- PDCA model and it was to be applied in situations when causes could be observed. Therefore, 5-whys was used as a systematic approach to observing the process. As such, it was an investigating process in which you would need need to go and see; rather than an analyzing process, where you can sit at your desk and analyze data to postulate what the “direct cause” probably is (which is appropriate when one is dealing with a problem situation that is complex, in which the causes are in a “black box” and you cannot see the direct cause.
This briefly summarizes my justification for the “5-Whys” method of cause investigation. So, that’s my story and I’m sticking to it!:-) (I’m sticking to it at least until I am presented with a better mouse trap.)
Thanks for the opportunity to join into the dialog! I hope that it was understandable/relate-able, and that it adds something to the conversation. I’m counting on hearing some feedback — don’t hold back…
Very well stated. I have and will us the 5 Why (or more Why’s if needed) . I also you the PDCA, DMAIC, Fishbone, etc…. Some tools work better in some cases then others. Sometime I use two tool to valid the first one used, or a combination of tools.
My basic believe is that the 5 Why is a good tool to teach people to “problem solve” (if you can teach that). I makes people ask question and think independently.
I believe there is some validity in the author’s critique of the 5-Whys method of finding the root cause, but it can and is a very useful tool to start on the journey to discovering and defining the actual root cause of a problem (Opportunity!). It can–and does—fall short if not used to its fullest extent, as discussed by some of the succeeding writers: It doesn’t have to STOP at just (5) whys, and there are several other LSS Tools in the toolkit to continue the transit to the Root Cause, such as a fishbone diagram as mentioned previously.
Just as you wouldn’t reach for a 9/16ths wrench to loosen a 3/4 bolt doing brake work on your car, you choose the appropriate tool for the job or task at hand. If the 3/4 bolts still couldn’t be loosened with the socket wrench and correctly-sized socket, you might choose a longer torque handle to expand on your ability to exert additional force on the offending bolt. And so on and so forth——-the key being you escalate your problem-solving efforts (and use of various tools) until the job is completed.
Brainstorming, fishbone diagram, controlled trials, and a small-scale proof-of-concept” can all be added to the basic 5-Whys Tool to arrive at concrete Root Cause conclusions—where appropriate.
The real key is don’t stop until you find the REAL root cause of a problem. Yes, it can—at times–make Management uncomfortable because the finger may point back to a bad decision that precipitated the issue, but I believe you will find the more thorough you are at tracing an opportunity back to the root cause, by taking the time and effort to correct it at the source, you may not only erase it forever, you may preempt a host of similar issues from ever popping up.
The problem with the 5 why’s is that it assumes there is a straight line to the root cause, what may work for simple problems, almost never does for complex ones. The major flaw is that it forgets the fact that the different components of any given systems are interralated.
I always prefer a method where I can see those connections and found particular appealing the Current reality Tree, a TOC tool conceptually similar to the Fault Tree Analysis.
I found the 5 why’s weak except for most of the rapid problem solving PDCA applications found on the floor in most companies that adopted Lean method.
In this line of thought I am not a big fan of the fishbone analys either that basically follows the same principle of the 5 why’s however, aggravated because in many many cases people stopps at the first or second level and call it done, struggling to apply appropriate corrective actions in many pseudo root causes.
Great comments above – thanks!
One of the misconceptions I run in to is that the answers to the 5-Why’s questions is a single answer. For a complex problem or one that the root cause truly is not known, there may be several answers. Many of the softwares used in 5-Why analysis promote this by using a linear set of questions and answers. I encourage people to go back to pen and paper, whiteboards, etc. Branch off when you need to with the 5-Why’s. When it’s all said and done, a good 5-Why analysis transforms in to an ishikawa diagram that you can take multiple actions with!
In my experience 5 Why’s usually works well when used as a complement of other problem solving tools. This tools should include information complementing the problem to ensure that the questions asked are the right ones (or close to them).
Something else that should be done is avoid asking questions by yourself. Do it in groups, diverse groups with people of involved areas in the problem and with different levels of experience; you’ll be surprise how many times the right questions are asked by people with less experience or close to GEMBA.
5 why’s generally for me is the last step after having developed a fishbone (Ishikawa chart) each end gets a 5 whys… there might more than one cause, or combination of causes. The fishbone helps keep more variables in mind making 5whys Lee’s subjective.
My issue with 5 why’s without: The Who, What, Where, When, How Much first are never more than educated guesses.
My 2nd issue with 5 why’s is, there are more than 1 corrective actions, which if not thought out in the same manner as a 5 why is a “trap” and get ignored.
Example:
EE slipped and fell OSHA recordable.
Why: The floor was slippery.
Why: The floor was wet.
Why: Another EE mopped with improper chemical.
Why: EE mopping didn’t dispense the correct chemical.
Why: The floor was wet.
Why: The EE didn’t see the wet floor sign.
Why: The EE wasn’t paying attention.
Why: The EE wasn’t wearing slip-resistant shoes.
Why: The EE forgot to change shoes.
Why: EE was rushed coming in to work.
In all cases, there is a process or a behavioral root cause that needs countermeasures put in place, but forced into 1 set of 5 why’s, the others are merely being prioritized as educated guess and may/may not be addressed. Depends on the skill set of the individual completing the 5-why.