5 Why and 5 Ws

4 minutes

Today, I present you two tools: the 5 why and the 5 Ws. Both are very simple to implement.

They can be used in problem solving, to find the root cause of a problem, or in goal definition. Since they were used in Greece and ancient Rome by philosophers, in their approach of systematic questioning, both those tools have proved their power.

I suggest you apply them to a much more pragmatic context: problem solving.

5 Why

When a problem arises, it is natural to ask the question, “why did this happen?” In order to find a solution and solve the problem. This tool goes further, once the answer to the first question is found, it questions why again, based on this answer, in order to find the original cause. It is a participative tool: to find the root cause, it is necessary to go to the place where the problem took place (zone of action, Gemba in Japanese) and to work with the people who are directly involved. To understand it, nothing better than an example:

  • Why did the operator slip?
  • Because there was oil on the floor.
  • Why was there oil on the floor?
  • Because the machine was leaking.
  • Why was the machine leaking?
  • Because preventive maintenance has not been done.
  • Why has preventive maintenance not been done?
  • Because the technician in charge is sick and absent.
  • Why did not another person replace the technician?
  • Because the maintenance range is lost and only he knows how to do it.
à retenir

The first question gives actions to set up immediately to prevent the incident from happening again. The iteration of 5 causes gives the root cause of the problem: the maintenance range is not available, in the absence of the employee in charge of the maintenance of this machine, no one can perform the actions and correctly follow the machine, which resulted in a small oil leak. It is by reaching the root that we make sure we achieve performance!

The iteration of the question why reaches the root cause to correct it.


This tool is also based on questions: Who, What, Where, When, How, Why. These different interrogative pronouns provide a deep understanding of the treated subject. Properly defined, the problem is simpler to deal with or the goal clearer to follow. Let’s continue the previous example with this method:

  • What are the machines that need a range?
  • Who knows the maintenance range?
  • What is the status of the maintenance ranges?
  • What is their level of update?
  • Who is responsible for the maintenance documentation?
  • Who could do the maintenance range?
  • What is the risk if we lose all ranges?
  • Who is the manufacturer of the machine?
  • Where are the range cabinets placed?
  • When was the last check of the ranges?
  • When can we write this range?
  • How can we write this range?
  • Why did not we notice his absence?
à retenir

Questions, “how much? ” and what for ? can complete this questioning.

Pourquoi, pourquoi, pourquoi ?


  • Why use these tools on a daily basis?
  • To characterize my problem and / or identify the root cause.
  • Why look for the root cause?
  • To effectively deal with my problem.
  • Why deal effectively with my problem?
  • To do the right thing right away and solve the problem definitively.
  • Why do right now?
  • To save time.
  • Why save time?
  • To read this blog and learn new tools / techniques.

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