The 5 Whys Technique: reach the root cause of a problem

The 5 Whys technique is one of the most simple and effective methods used to reach the root cause of a problem.

It is widely used in industrial and service companies; it’s a tool that is very connected to total quality and continuous improvement.

The secret of the whys 5 technique is of its practicality and effectiveness.

When faced with a problem or nonconformity, you should ask yourself why it occurred and then ask again about the answer and so on until you reach the fifth why.

Created by the famous engineer, Taiichi Ohno one of the main proponents responsible for creating the Toyota production methodology, the 5 Whys technique has a clear objective: to determine the root cause of a problem.

In this post, we will explain in more detail these and other concepts of the 5 Whys technique and how to use it in your daily lives, whether at work or even in other fields of activity.

See more on the 5 Whys technique: Mapping Activities and Streamlining Processes 

The whys of the 5 Whys technique

Let’s start with the definition of root cause:

It is the first cause, the original issue that gave rise to the problem.

With this sequence of five questions looking at why something happened, Ohno managed to get people to break away from the very common and difficult to eradicate habit in human behavior: Confusing the cause of a problem with a feature or a symptom of it.

For example: Let’s say you want to use your car in the morning and upon trying to leave you to discover that the car has a fault, it won’t start. By asking why it won’t start, discfind out thatthe battery is flat.

So, you come to the conclusion that the car is defective because the battery is flat.

But no! In fact, the flat battery is not the cause of the fault; it is just a part of it!

You need to find out why the battery went flat. And continue until reaching the root cause.

The battery could be flat because you forgot to turn off the lights the night before, or there’s a battery manufacturing defect, or something more difficult to detect, such as an error in the cars software or even due to a short circuit caused by a wire that is contacting another.

Imagine that you simply replace the battery and, the next day, the car again does not work. If you had continued the following questions to the fifth Why, you might have discovered that the battery is flat because, for example, there’s a defect in the car’s software, then you would have taken it to the mechanic, who would have asked why the software was defective and reinstalled it correctly.

Then he would report the fault to the factory, to find out if that particular software installed in your car was wrongly programmed (and why it went unnoticed by quality control) or if in fact every car with this software installed will present the same problem sooner or later and if they need to recall cars from this factory.

Wow! Such a long example of the 5 Whys technique!

Why 5 Whys?

That’s a good question. Why not 4 or 6? In fact, after using the method Ohno often concluded that 5 was the average number of times it was enough to get to the root cause of a problem. 4 whys might be necessary sometimes and, in other cases, 6 or 7. But the ideal number is most often 5.

The 5 Whys Technique and the Ishikawa Diagram

Also known as the fishbone diagram, this methodology was developed by Ishikawa, it uses a diagram shaped arrow showing the possible causes of a problem, but divided into 6 fields of analysis:

  • Method
  • Material
  • Labor
  • Machine
  • Measurement
  • Environment

Then, for each of these causes for each field, ask the 5 Whys questions. Filling up a range of causes that can be resolved is an excellent source of information for improvements in production processes or the delivery of services.

As you have seen, though old, the 5 Whys technique can provide important answers during process design, especially if aided by BPM software that can give you accurate information in real time, helping you to respond more assertively to each of the 5 sequential questions: – Why?

2 Comments. Leave new

  • Bonjour,
    je souhaite utiliser la méthode des 5 S ans un cas pratique à traiter. Mais les informations de mon cas me permettent de n’arriver qu’au 3ème pourquoi. Est-ce que je peux m’arrêter là? quelle autre méthode vous pouvez me conseiller?

    February 25, 2021 8:07 pm

    This document is so important for me. May you produce more


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