The 5 Whys Method: Getting to the Root Cause Quickly

Jonathan Trout, Noria Corporation

The 5 Whys tool is the straightforward process of asking "why?" in an interrogative fashion to get to the root cause of a specific problem. Read about when and how to use 5 Whys, see 5 Whys examples and more.

5 Whys  

What Is the 5 Whys Tool?

The 5 Whys tool is the straightforward process of asking "why?" in an interrogative fashion to get to the root cause of a specific problem. Each answer to a "why?" question forms the basis of the next question, leading to five iterations needed to resolve an issue. This technique helps you dive into and discover how smaller issues have an underlying cause-and-effect correlation to a root cause. While it can be used as a standalone tool, the 5 Whys method is often used in cause-and-effect analysis tools such as a root cause analysis and the "analyze" phase of DMAIC (define, measure, analyze, improve and control).

As with most lean techniques, the 5 Whys tool was originally developed in the 1930s by Sakichi Toyoda, the founder of the Toyota Motor Corporation. It was soon introduced as a training staple in the Toyota Production System (TPS) in the 1950s. The architect of the TPS and creator of lean manufacturing techniques, Taiichi Ohno, said the 5 Whys method is the basis of Toyota's scientific approach and that by repeating "why?" five times, the root cause of a problem, as well as a solution, becomes clear.

Whenever a problem cropped up, Ohno encouraged his staff to explore problems firsthand until the root causes were found. "Observe the production floor without preconceptions," he would advise, according to a Toyota company website. "Ask 'why?' five times about every matter."

When to Use a 5 Whys Analysis

Imagine the often-humorous example of children continuously asking "why?" after each answer you give them. Just while driving down the highway, your child may ask questions ranging from "Why is the moon not shining anymore?" and "Why aren't there any clouds in the sky?" to "Why are we going to the grocery store?" As annoying as this can be at times, from the ages of two to five, kids ask around 40,000 questions, with most of them being explanatory-seeking in nature, according to Harvard-based child psychologist Paul Harris. The reason for this? It's not to annoy you, but rather they simply want an explanation.

This is the basis of the 5 Whys method, which not only is helpful as an analysis tool but also is commonly used for troubleshooting, problem-solving and quality improvement for simple to moderately difficult problems. Put simply, it helps explain why something is happening. The 5 Whys tool tends not to be the best method for more complex issues because it typically leads you down a single path or a few paths of questions, and with complex issues, there may be multiple causes. Cause-and-effect analysis (fishbone diagrams) or failure mode and effects analysis (FMEA) may be more effective tools for complex issues.

For moderately simple problems, 5 Whys is a great way to get to a root cause quickly without having to use a lengthier, more in-depth approach. Its simplicity makes it a flexible tool to use with other lean methods and techniques like performing a root cause analysis, kaizen and Six Sigma.

Some issues may have more than one contributing root cause, so even though the 5 Whys method is best for simple to moderate issues, it's still useful when there are a few underlying issues plaguing the same problem. When a 5 Whys investigation branches out into multiple paths, it's sometimes referred to as a three-legged 5 Whys. If a few paths present themselves during a 5 Whys investigation, it usually means there is ineffective detection control or a systemic issue. Therefore, the additional paths of the three-legged 5 Whys are useful to determine what control or process wasn't in place or isn't effective in detecting an impending failure.


How Do You Use 5 Whys?

The 5 Whys method is very straightforward to put into practice, essentially determining a problem and asking "why?" five times (sometimes less, sometimes more) to get to a root cause so you can fix it permanently. There's a simple six-step process you can follow each time to ensure you're getting the most out of the 5 Whys method. It starts with forming an appropriate team and ends with taking corrective action.

5 Whys steps
  1. Get a team together. The 5 Whys method is not an individual-based exercise. Best practice dictates you should assemble a cross-functional team of employees who are familiar with the process in question. This allows for unique viewpoints as you begin the process of determining the root cause.

    It sometimes may be helpful to assemble your team after you've identified and defined the problem (step two). The thinking behind this is it's important to include all team members who were affected by or noticed the issue because they have firsthand knowledge about what's happening.

    Once the team is assembled, choose a team leader to facilitate the discussion, ask the 5 Whys, take notes and eventually assign responsibility for the solution(s) the group identifies. There are no qualifications to be a team leader, and it doesn't necessarily need to be the person who initially discovered the problem.

  2. Define the problem. As previously mentioned, this could be considered step one, since a problem is what kicks off the 5 Whys process in the first place. If possible, have the entire team observe the problem in action. If not, rely on team members who experienced the issue firsthand. Once the problem is discussed, write a clear problem statement on which everyone can agree. For example, "The cans are moving down the canning line with torn labels," or "The newsletter isn't being sent out on time."

    Once the problem is clearly defined, write it on a whiteboard or sticky note and place it for all to see, with enough room around it to add your team's answers to the "why?" questions.

  3. Ask "why?" Now it's time for your team to ask why the problem is happening. For example, why are cans moving down the canning line with torn labels? Despite its simplicity, asking "why?" requires some serious thought among the team. It's important to search for answers that are rooted in fact(s); that is, the answers to the "why?" questions must be things that have actually happened, as opposed to guessing what might have happened.

    Making sure the answers are based on facts prevents the 5 Whys from becoming a deductive reasoning process, which can lead to a massive number of possible causes and create confusion due to newly formed hypothetical problems.

    Your team may come up with one obvious reason why or several possibilities. Write each answer below the problem statement in clear, brief statements rather than single words or a lengthy phrase. For example, saying "The pressure-sensitive labeler is creating too much pressure" is better than a vague "The labeler isn't working properly."

    Try to dig down at least five levels with five "whys?" questions. It might only take three before you determine a root cause. While it may seem natural and even beneficial to take every path that presents itself, this can open up too many corrective action options. The purpose of the 5 Whys is to be a lean process in which picking one path allows you to settle on just the right amount of corrective action needed to solve a problem. If the same problem happens again, you can do the 5 Whys process again and go down a different path.

  4. Learn when to stop. You'll know when to stop asking "why?" when asking that question no longer generates useful responses. If you haven't gotten to the root cause of the problem, you may want to consider a more in-depth problem-solving method like FMEA or cause-and-effect analysis. If you've identified more than one cause in step three, repeat the 5 Whys method for each of the different branches until one root cause is reached for each one.

    It's also important to ensure you haven't stopped too soon and aren't just accepting a knee-jerk or gut reaction. Take it to the point where no useful responses are being produced by the team.

    Finally, you may discover the root cause of the problem is that someone failed to take a necessary action. The 5 Whys method lets you bypass placing blame and ask why that happened. Often, you'll find an underlying organizational issue or an area where the process needs to be improved.

  5. Take corrective action. Once everyone has agreed on a root cause, you need to identify countermeasures that will prevent the issue from happening again. For example, you may go through each "why?" question-and-answer pairing and come up with a corrective action for each one. Once a corrective action is decided upon, the team leader should assign the solutions to the appropriate members.
  6. Monitor and audit your correction actions. As with any newly implemented corrective action or process, it's important to make sure it is doing what you'd hoped – fixing the problem. In this case, monitor the corrective action to see if it's working or if you need to amend or replace it. If you discover it's not working, repeat the 5 Whys process.

5 Whys Template and Examples

5 Whys flow chart

Let's take a look at the 5 Whys method in action using a couple of examples.

Problem statement: The newsletter didn't go out on time.

  1. Why didn't the newsletter go out on time?

    a. Article submissions weren't submitted on time.

  2. Why weren't article submissions submitted on time?

    a. Because the freelancers' assignments didn't go out on time.

  3. Why didn't the freelancers' assignments go out on time?

    a. Because the freelancers are new and hadn't submitted a signed non-disclosure agreement (NDA).

  4. Why hadn't the freelancers submitted their signed NDAs?

    a. Because they weren't onboarded properly.

  5. Why were they not onboarded properly?

    a. Because the new editing assistant isn't familiar with the onboarding procedures.

You now can see that the root cause of the newsletter not going out on time was actually due to a lack of training for the new editing assistant whose job is to coordinate with all freelancers, not the more obvious reason of the freelancers missing their deadline.

Let's look at another example:

Problem statement: A maintenance technician slipped and injured himself during a routine inspection.

  1. Why did the maintenance tech slip during a routine inspection?

    a. There was an oil leak near the machine on which he was working.

  2. Why was there an oil leak near the machine being inspected?

    a. A seal in the machine deteriorated, causing cracking and leaked oil.

  3. Why was the seal in the machine deteriorated and cracking?

    a. The seal was not strong enough for the application in which it was being used.

  4. Why was the seal not strong enough for the intended use?

    a. A cheaper seal was purchased from a new supplier.

  5. Why was a cheaper seal purchased?

    a. The type of seal and seal material were not specified in the service manuals.

At first glance, the cause of the injury to the maintenance tech seems to have been related to improper maintenance or inspection practices, but the root cause actually goes a little deeper. It's essential the progression of your questions and answers follow a logical path. One way to ensure this is to read the answers (or causes) in reverse order. When read in reverse, they should follow a logical progression all the way back to the problem statement. See below:

  • The type of seal and seal material were not specified in the service manuals.
  • Because of this, cheaper seals were purchased from the new supplier to reduce costs.
  • Because of this, the seal and seal material were not strong enough for the application in which it was being used.
  • Because of this, a seal in the machine being inspected deteriorated, cracked and began leaking.
  • Because of this, oil leaked out onto the floor.
  • Because of this, the maintenance technician slipped and was injured during a routine inspection (problem statement).

Limitation of the 5 Whys Technique

The 5 Whys method is a great technique for getting to the root cause of a problem in a rather short period of time; however, its speed and ease of use sometimes can lead to unbalanced results when it comes to a recurring failure if the 5 Whys fail to produce the true root cause. A few limitations of the 5 Whys are as follows:

  • It doesn't always lead to the identification of the root cause when the cause is unknown to team members. In other words, if the team doesn't have the necessary knowledge or expertise to identify the cause, no one will make much progress.
  • It doesn't always lead to the identification of the root cause when the cause is unknown to team members. In other words, if the team doesn't have the necessary knowledge or expertise to identify the cause, no one will make much progress.
  • It may encourage stopping the analysis when symptoms are discovered, instead of diving deeper to determine the true root cause.
  • Confirmation bias – the tendency to interpret new evidence as confirmation of one's own existing beliefs or theories – tends to be a driving factor for some team members during analysis. This means some team members may favor or only identify causes that match the root cause they believed was responsible for the problem from the start.
  • You must have support from experts or a knowledgeable team leader to make certain the team is asking the right questions. To help prevent a biased conclusion, it's a good idea to include subject-matter experts on your team along with those involved in the actual issue. Subject-matter experts can help minimize the risk of one-sided conclusions while still having the knowledge to provide a fair analysis.
  • Team members tend to rely on deductive logic instead of observation when identifying factors leading to the root cause, which can produce poor results.

What the Coronavirus Can Teach Us About Asking "Why?"

COVID-19, a new illness caused by the coronavirus, has been dominating the news recently because of its rapid spread into a worldwide pandemic. It presents symptoms similar to the common flu we experience every year, so why the panic? One of the main reasons for urgency with the new coronavirus is because the Centers for Disease Control and Prevention (CDC) initially wanted to get to the root cause of the virus and prevent it from spreading and becoming another common worldwide virus like the flu – one which we now must continuously treat the symptoms.

5 Whys and the coronavirus

You may recall SARS (severe acute respiratory syndrome), which is another coronavirus that had a similar story. In 2002, it popped up in China and spread worldwide within a few months. However, in this case, the disease was quickly contained and is all but eradicated with no known transmissions since 2004.

So, what's the difference between the two outbreaks? It's suggested that while there are striking similarities between the two coronaviruses, COVID-19 might have different characteristics, making it more difficult to contain with the same methods used for SARS. It differs from SARS in terms of infectious periods, transmissibility, severity and the extent of its spread within communities. SARS was contained fairly quickly by essentially working backward and asking "why?" and "how?" it was spreading. This helped the CDC contain it and come up with preventable methods, like specific travel alerts. COVID-19 seems to be spreading more rapidly, and we simply couldn't ask "why?" fast enough in order to contain it.

In the world of business and manufacturing, where efficiency and time equal money, it can be maddening when you're faced with a recurring problem. Dealing with the same issue(s) over and over is time-consuming and a waste of valuable resources. Often, these issues boil down to the fact that no one is taking the time to identify and address the root causes before they become repeatable and, in some cases, lead to other issues. Just as we are seeing with COVID-19, the symptoms are treatable, but the treatment just becomes a mitigation tool to temporarily stop an issue from occurring until it happens again.

Just like the goal of stopping a major disease from spreading into a pandemic by asking "why?" and "how?" to find the epicenter, the goal of the 5 Whys method is to quickly get to the root cause of a particular issue so it doesn't become mainstream.

Subscribe to Machinery Lubrication

About the Author