Method

What is Ishikawa Diagram?

Fishbone

In 30 seconds

The Ishikawa (fishbone or cause-and-effect) diagram is a tool that visually organises the possible causes of a problem under categories. Categories commonly used in manufacturing are known as the 6Ms.

How does it work?

  • The problem is written at the head of the fish.
  • The bones are categories: people, machine, method, material, measurement and environment.
  • Possible causes are gathered under each; candidates are then verified or eliminated.

Often confused with

Diagram and analysis

The diagram lists possible causes; it does not prove the root cause. Verification is a separate step.

Common mistakes

  • Inventing causes just to fill every category.
  • Completing the diagram and never testing any candidate.

From a QWorks perspective

In QWorks Ishikawa candidates are marked one by one with an OK/NOK decision; why each was eliminated stays visible with the record.

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