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Ishikawa or 6M Diagram

Kaoru Ishikawa (1915-1989), Japanese chemical engineer who invented the diagram of cause and effect which is one of the essential instruments of problem solving. This diagram, in the shape of a fishbone, shows the relation between an observed effect and its causes.


The effect observed must be perfectly defined thanks to QQOQCCP (see definition).


  • Define the potential causes listed through brainstorming and distribute them by family according to the 6M (Manpower, Machinery, Materials, Method, Mother Nature, Measurement).
  • Go out on the field and confirm the potential causes through observation (Gemba, Gembutsu, Gemjitsu).
  • Eliminate the potential non-confirmed causes.
  • Choose the causes to be analyzed.
  • Go back as far back as possible to the root causes (5 Whys?).
  • Visualize the real causes quantified on the diagram.


This method is used in the training course: Structural Method of Problem Solving.

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