Method

What is 5 Why?

In 30 seconds

5 Why is a simple root-cause technique that deepens the cause of a problem by asking "why?" repeatedly. The number five is not a rule but a reminder not to stop at the surface.

How does it work?

  • The problem is written as a single, fact-based sentence.
  • Each answer becomes the subject of the next "why?"; the chain stops when it reaches a controllable cause.
  • Separate chains for occurrence and escape are recommended.

Often confused with

5 Why and Ishikawa

Ishikawa spreads out possible causes broadly; 5 Why deepens a selected one. They are often used together.

Common mistakes

  • Filling answers with assumptions without checking each link against data.
  • Ending the chain on a personal cause such as "carelessness".

From a QWorks perspective

In QWorks the 5 Why chain is kept in the case’s problem-solving step; the cause it reaches is verified with a decision and evidence.

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