The 5 Why Problem-Solving Technique | Root Cause Analysis

Washington Monument Problem Solving 5 Why
5 Why Problem Solving Analysis

5 Why Problem-Solving Technique

One of the most famous and straightforward problem-solving methodologies introduced by Toyota has become known as the “Five Why’s”. It’s a tool where you simply keep asking “Why” 5 times to identify the root cause of the problem and potentially a simple solution. It’s at the heart of lean thinking and our Lean training courses.

Did you know that kids ask around 90 questions a day and many of them are just “Why”!

We all naturally ask, “Why” all the time? The last figure I heard is that kids ask around 90 questions a day, and many of them are “Why?” style questions.

And the best way to imagine how the ‘Five Whys’ work is to imagine children asking “why”… again and again. As adults, we ask “Why?” once or maybe twice. If you are at a dinner party, asking your friends “Why?” more than twice, may make us look like petulant children. To ask your boss “Why?” once may not even be possible in case it comes across threatening or disrespectful, or perhaps you will feel that its a sign of your lack of knowledge.

But asking “why” without the threatening and undermining tone is an essential way we all began to learn. Asking “why” almost gets kicked out of us at school and with it the questioning mind that we all need if we want to do something different.

As a parent, I know the feeling in the car when your child in the back seat asks a question. The response I give just does not satisfy their curiosity. They are trying to order a particular bit of information in their brains, and my answer never worked. So they ask “Why?” again.

It does not take long within this cycle of asking “why?” before we all begin to have difficulty to answer. We twist our logic as we try to justify why we said what we said in the first place … “but why?” just keeps on coming and before you know it we end up tongue-tied and just putting our foot down with “STOP! That’s just how it is! Alright”

The ‘Five Whys’ is this simple in theory.

It asks us to take an open mind to a problem and to not be afraid to keep asking why five times (plus or minus a couple depending on the situation). And what is the goal? Well, our goal is to keep drilling down until we feel that “A-HA!” moment when things suddenly make more sense, and we have uncovered a root cause.

5 Whys Example for Training

Washington Monument 5 Why Analysis

So let’s bring this to life with a real-life example regarding the Washington Monument.

The Washington Monument and others for that matter were deteriorating quite severely in the early ’90s. The specialists were sure why. However, on the desk of Don Messersmith, an esteemed Entomologist (the scientific study of insects) was what has become one of the most famous examples of the five whys approach to problem-solving.

Just for the curious: Messersmith, Donald H. 1993. Lincoln Memorial Lighting and Midge Study. Unpublished report prepared for the National Park Service. CX-2000-1-0014. N.p

The problem was simple: The Washinton Monument in Washington D.C. is deteriorating.


Why #1 – Why is the monument deteriorating?

  • Because harsh chemicals are being frequently used to clean the monument

Why #2 – Why are harsh chemicals needed?

  • To clean off the large number of bird droppings being left on the monument

Why #3 – Why are there a large number of bird droppings on the monument?

  • Because of the large number of spiders and other insects which are a food source of the birds

Why #4 – Why are there large numbers of spiders and other insects around the monument?

  • Because the insects get drawn to the monument at dusk

Why #5 – Why are the insects attracted to the monument at dusk?

  • Because the lighting in the evening attracts the local insects

This classic five why example shows how the goal of the “five why problem-solving” approach is to move past the first level inquiry. It would have been quite easy to change the chemical, which was causing the apparent issue or investigate different cleaning methods which may slow the deterioration but nothing more.

The solution implemented was simply to delay turning on the lights at night. The result was a dramatic 85% reduction in the midges and consequently, a massive drop in bird droppings and the level of cleaning required. The bonus was also a reduction in energy costs.*

5 Whys Example for Design Thinking

5 whys diagram

Five Why application to Customer / User Experience

The five why problem-solving technique can be used in almost all scenarios where you are trying to resolve an identified problem. So in the example below, let’s look at customer behaviour.

In the book “Hooked (How to Build Habit-Forming Products)”, the author Nir Eyal (, uses the five whys approach to dig into users behaviour and tries to identify the underlying root cause of the behaviour. He points out that “one method is to try asking the question “Why?” as many times as it takes to get to anemotion.” The emotion behind the behaviour is often the driving force and the trigger which forms habits.

Problem: What drives people to use email?


Why #1 – Why would Julie want to use email?

  • So she can send and receive messages.

Why #2 – Why does she want to do that?

  • Because she wants to share and receive information quickly?

Why #3 – Why does she want to do that?

  • To know what’s going on in the lives of her coworkers, friends, and family.

Why #4 – Why does she need to know that?

  • To know if someone needs her.

Why #5 – Why would she care about that?

  • She fears to be out of the loop

While the final “why” appears to point to something very different than the Washington Monument example they both uncover a root cause. 

The first example is that the lighting is attracting the midges.

In the second example – its finding the root emotion that drives people to use a particular product and knowing that this emotion can help business connect with their customers at a deeper level to build successful products that a customer wants to engage with.

“Here is Edward Bear, coming downstairs now, bump, bump, bump on the back of his head, behind Christopher Robin. It is, as far as he knows the only way of coming downstairs, but sometimes he feels that there really is another way, if only he could stop bumping for a moment and think of it.” – Winnie the Pooh

Advantages and Disadvantages of 5 Whys

The “5 Why” remains one of the most straightforward tools to remember, and it’s easy to put into practice. However, the simplicity hides a level of complexity.

Like many of the best and simple tools, they need to be tested and practised to get the best from them.

One of the key disadvantages of the tool is that teams only follow one avenue of investigation rather than focusing on all the potential causes to identify the real root cause. This is not really an issue with the tool, but the way people implement the tool and rush through things.

Another potential disadvantage is that all too often the teams never get anywhere near 5 Why’s. Once again, an issue with the implementation rather than the tool. Teams quickly get overexcited and stop at 2 or 3 Whys as they have jumped to a solution that looks great.

So always try to get to 5 and be brave and follow every avenue of investigation.

And remember, this is processed focused, so try to avoid the trap of seeing people’s capability and training as the single root cause.

If you end up with lots of “more training is required” as a solution, then go back up and try again and see if anything has been missed from a process point of view. Why is the process so hard to follow?

In our experience, any issue or problem can be quickly improved by asking why within a small group. It has helped teams better understand their customers’ needs, and it has helped organizations save thousands of dollars on fixing the wrong thing.

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5 Why Method - Summary

  • This is a team exercise and asking the why needs to be explorative and not in any form understood as a criticism. So keep the ideas and conversation open with strong ground rules and group facilitation.
  • For each Why there may be multiple reasons and each of these need to go through a separate set of 5 why discussion. You will then need to prioritize the potential root causes either through a Pareto or through a simple voting system initially to understand which ones the team believes need to be investigated first.
  • Keep in mind that we are focused on processes and not always people. Remember the 94/6 rule – that 94% of the issues come from your process and 6% of the issues from the people. So if you end up with more training as the root cause, take it from me, you have missed something major.

Summary: 5 Why Problem Solving Technique

When conducting five why’s, they are never quite as neat as the examples above. Each time you ask why there will rarely be only one reason. You are much more likely to end up with 10 to 15 different potential root causes. As a team, you can then work through the possible root causes and with testing, piloting or perhaps through a simple team vote, begin to prioritize solutions.

The below slide from our Lean Six Sigma training deck visually captures how five why’s work in reality.

5 Why Example Template for Training

* A quick footnote on the Washington Monument

Like many real improvement opportunities, the hardest part is change management. And the Washington Monument is not the exception. With the delay in turning on the lights, the side effect was the iconic tourist photographs of the monument at dusk vanished. The complaints started to arrive. Even from the cities inhabitants complaints. 

While a solution had was found to stop the use of heavy cleaning chemicals, this monument was a landmark and symbol of the city. And it was not too long before the lights were back on and the government was looking for a new solution.

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  1. Very good article! Thanks for sharing. One correction though- on the 5th why for the Washington Monument answer I do believe you meant to put “attract” and not “attack”? Please keep sharing your insight. This helps in my lean thinking and gives more tools in the tool box. Thanks, Bill

    1. Thanks, Bill – appreciate the comments. And yes, definitely meant attract!

  2. This is a great article, thanks for the share

    1. Thanks Sophie – Appreciate the feedback.

  3. […] Question is to delve into what can be done better to improve things and that begins by some basic 5 Why Problem Solving to highlight the root […]

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