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Cause-and-Effect Diagram

The cause-and-effect diagram, also called “fishbone” or the “Ishikawa diagram” (named after its inventor), permits identification and organization of a list of factors thought to cause a problem or affect variation in a desired outcome. The cause-and-effect diagram is essentially a pictorial display of a list. Each diagram has a large arrow pointing to the name of the problem or issue. The branches off the large arrow represent main categories of potential causes. Smaller branches, representing sub-categories (can be a list of items) are then drawn off of each major branch.

The Fishbone Diagram can also be used as a Root Cause Analysis Tool. A combination of the Affinity Diagram and the Cause and Effect allows the generation of ideas, in a brainstorming fashion, then the clustering of the ideas around the “Bones.”

These main categories (“Bones”) may be customized to fit the process under study, however, typical categories of major causes used with the cause-and-effect diagram are:

  • Equipment, Methods, Materials, People, Environment/Measurements/Procedures
  • Steps of Process (Block Diagram)
  • Who–What–When–Where
  • People, Provisions (Supplies), Procedures, Place, Patrons (Patients)