Asking why several times after each other is often something experienced with small children, but it also is one of the techniques used in the analysis phase of Six Sigma and is called 5 Whys.

Background of 5 Whys

It was within Toyota Motors the 5 whys was developed, and then used as part of their problem solving. The foundation of the approach was that by asking why five times, the root cause of the problem and its solution becomes clear.
Today the 5 Whys is used widely across different industries around the world.

Example of 5 Whys

Below is an example of a 5 Whys performed after an employee in the plant slipped and fell while performing their regular duties.

  1. Why? – There was oil on the floor.
  2. Why? – The machine in that cell was leaking oil.
  3. Why? – A pressure fitting on the machine failed.
  4. Why? – Inspection of hoses and fittings is not part of the preventive maintenance (PM) schedule.
  5. Why? – The PM system does not consider Equipment Manufacturer’s recommendations to develop PM schedules.

Don’t stop with “Because we don’t have enough people, money, time…
Solve the problem with the people, money, time you DO HAVE.

5 Whys used with Fishbone Diagram

The 5 whys can be used individually, but also as part of a Fishbone Diagram (Also known as Cause and Effect or Ishikawa Diagram). The fishbone diagram is used to identify all the potential causes of a problem. 5 Whys can then be used on the potential causes to uncover the root cause of the problem.

Benefits of 5 Whys

  • Can identify the root cause of a problem
  • It is a simple tool that can be used without knowledge of statistical analysis.

If you are interested in 5 Whys and structured problem solving, then our 8D Problem Solving Training might be interesting for you.
It is a detailed training on how to effectively solve problems and prevent them from reoccurring, and cover the use of 5 Whys as part of the training.

Alternatively you can continue to our quality training page for an overview of the training we provide.

Go to Quality Training

The 5 Whys Analysis