5 Why? Simple but effective lean tool

Just like any good mechanic, a good lean expert should have many tools to help them do their job. While a mechanic may be fixing something under the hood of a car, a lean expert will be fixing something under the hood of a business. Unlike a mechanic’s troubleshooting, sometimes the real reason why something is not functioning inside a business isn’t readily apparent, and there isn’t a manual to troubleshoot it. Additionally, it may be masked by other problems that appear to be the real reason, or “root cause”, when in truth, it is only a diversion.

Avoiding this is a very important job of all people who work in a company, primarily a lean expert, or someone who works on the quality team. There are many ways in which the quality team can approach the problem, and the 5 why technique is one of them. It is designed to help get to the real root cause of a problem, so the cause can be addressed through a short term or long term corrective action. The corrective action, then, can be tracked for its effectiveness.

The 5 why system is one in which the simple question “why?” is asked at 5 different levels of a problem to get to the bottom of the situation. It was first used in the early 1970’s by the Toyota Company, who is often credited with being the pioneer of modern quality.

If used correctly, it can provide a way to help identify the true root cause of the problem by using a feedback system. An added benefit is that it can be used both on an individual basis as well as a part of a group attack. It can, and should, also be integrated into the Kaizen, lean, and Six Sigma methods.

It can also be used in conjunction with other tools, such as root cause analysis software and fishbone diagrams to help aid in the discovery of the true root cause and identifying the cause and effect associated with it. While some other root cause analysis tools are complex and require experts to run them, even a two year old knows how to ask the question “why”, so the much more simplified approach is easy to adopt to the level of each individual worker.

Of course, it may seem like the five why method is too good to be true: a simple, effective way to approach complex technical issues that anyone can apply? This is the exact argument that most “five why” critics have used against the system: it is not as effective as thought.

The biggest argument is that, while it is purported to get to the foundation of the problem, in reality, most people stop at the surface level symptomatic issues that appear to be plaguing them on a daily basis. By asking the question “why?”, most will simply come up with another symptom instead of working their way back to the root cause. They will then fix the additional symptom, proclaiming to have found and corrected the root cause, when in fact the problem they were trying to solve never actually is fixed.

Another pitfall that the critics of this system claim detracts from its effectiveness is the tendency for personnel to stop at their level of knowledge or comfort, instead of digging deeper and thoroughly investigating the limits of their technical knowledge. It is too easy for the “five why” method to reward and promote the “quick fix” answer of simply satisfying the question “why”, instead of more thoroughly finding a technical answer.

Lastly, while simplicity is one of the merits of the system, it is also purported to be one of the downfalls. Because anybody can conduct the five why method, they actually do, and do not seek professional assistance in determining whether the “why” they submit is a true, actual “why” and not a surface level quick fix.

Lean Tools Series - 5 why technique


Figure (1)

Figure (1) illustrates the typical conduct of solving the answer “why does the pump leak”. As can be seen, it addresses the fact that the seal inside of the pump bell housing is leaking fluid. While many companies and employees would stop there, instead, this technique requires the champion to go much further and address the reason why the seal leaks.

Of course, there can be more than one “why” to every reason, as demonstrated by Figure (1). The seal could leak because of improper installation of the seal, or possibly an inadequate seal design. Each one of those has their own “why” branches, which address the more subsurface issue causing the “why” before it.

As stated earlier, anyone can use this method. However, care and consideration should be taken to at least fully train the personnel who will be in charge of leading the five why inquisition, as it is very easy to scratch the surface of the challenge and never actually dig to the subsurface root causes.

The 5 why technique is a great tool when used in conjunction with other tools as an aide in finding the root cause of a problem. Like any other tool, it should be wielded by someone who understands how to thoroughly investigate problems and conduct a solid root cause analysis.

Cause and effect diagram (Ishikawa Diagram)

A company has a problem that they need solving. For sake of example, it is a quality issue. So the company gathers a team together to figure out what is happening to truly cause this problem. They have all heard of a “root cause analysis”, and would like to find the true root cause that is causing this problem. They gather together in a room and start to brainstorm what the possible causes are. But they quickly realize that their brainstorming session isn’t focused at all, but they keep going.

They come up with what they think is the true root cause, and find a corrective action for it. They implement the corrective action, only to find out later that while they have helped the problem, they haven’t actually found or fixed the root cause. This is the hazard of not using the cause and effect diagram during a root cause analysis.

A cause and effect diagram, simply put, provides a way for the average manager or office worker to be able to effectively come up with a true root cause of a problem. It is a process that can be repeated by anyone with a basic level of understanding of the system or the processes involved. It also allows the team to be able to approach extremely complex problems and situations by breaking it down into the fundamental components of what usually goes wrong in most situations.

The first cause and effect diagram was created in 1943 at the Kawasaki Steel Works to depict the work factors involved with a process. Because of this, they are sometimes called Ishikawa diagrams, after the original presenter, Kaoru Ishikawa. They are also called fishbone diagrams in some circles because of their resemblance to fish bones.

It is very uncommon for a quality problem, or any problem in today’s high tech world, to be simple. Often, they contain many different factors and interactions that are hard to conceptualize when sitting in a meeting room. A cause and effect diagram breaks these complex problems down into easier, more simplified components, so they can each be individually addressed for determining their root cause.

A good diagram will break down the issue into major causes and sub causes, leading to the eventual discovery of root causes, which is the end goal of all six sigma processes. It will also provide a visual understanding of the problem for all parties involved, leading to a better understanding of the problem, and provides a way to focus on the correct issues to discuss and analyze.

Cause and effect diagram (Ishikawa Diagram)

Figure (1)

There are very few instances of brainstorming sessions that should not include a fishbone diagram. An example of a fishbone is contained in Figure (1). The cause and effect diagram should always start with the effect that you wish to change on the right side of the paper, in the case of the above example, the “Leaking Pump”. You should then draw the backbone of the fish, a horizontal line from left to right. Include the primary causes, or even just a general category of cause on diagonal lines that are alternating between above and below the backbone of the fish. This can be seen in Figure (1) by the categories of “Leaking Seal”, “Leaking O-Ring”, “Misaligned Leakage”, “Improperly assembled seal kit”, “Environmental”, and “Ruptured Seal”.

From those lines, you should branch off into additional diagonal lines that indicate the secondary causes, or the causes of the primary causes. For example, in Figure (1), the “Static vs. Dynamic” and “Cold Weather” causes are the root causes. From there, you can branch off a third time from each secondary cause, which will indicate the root cause that should be addresses. Not every secondary cause is going to have a root cause, as the secondary cause is sometimes the root cause of the problem. Figure (1) doesn’t have any third level causes, as the second level each contain the true root causes.

Once you have done this, you should have a good, thorough, cause and effect diagram. From here, you should mark the causes that you plan on correcting, and then brainstorm a corrective action, or many corrective actions, that will address the root cause. Theoretically, if the root causes of a problem are eliminated, the problem will either disappear, or be dramatically reduced. In reality, what happens in many situations, is that the problem changes into a new problem with the same symptoms, making it look like the root cause was not the true root cause. What actually happens is that the root cause changes, but causes the same problem. Many times, the reason for this is that the new root cause was being masked by the bigger, original root cause.

Many companies require all of their employees, from the hourly worker to the CEO, to be able to correctly make a fishbone diagram and participate in the root cause analysis. It is a simple process that can be understood by all, yet can lead to dramatic changes for the better. It is in a company’s best interests to be able to fix a lot of their problems by using the cause and effect diagram by any and all personnel.

If a company is interested in a process that is simple, straightforward, and more often than not attacks the root cause of the problem, all employees should be well versed in creation and execution of a fishbone, or cause and effect, diagram.