StATS: How to draw a fishbone diagram (March 8, 2007). Category: Quality control

This is a condensed version of a handout

that I have used in previous training classes.

The fishbone diagram (also called the Ishikawa diagram, or the case and effect diagram) is a tool for identifying the root causes of quality problems. It was named after Kaoru Ishikawa, the man who pioneered the use of this chart in quality improvement in the 1960's.

If you want to use a Fishbone Diagram, first list the main problem on the right hand side of the paper. Then draw a horizontal line to represent the "backbone" of the diagram. This line is not labeled. Off of the backbone, draw and label major bones: 4 to 7 major categories of causes. A commonly used list of major causes is Management, Manpower, Machines, and Materials. Another possible list is Policies, Procedures, Plant, and People. Then elicit ideas using an approach like brainstorming to place individual causes as minor bones on each major bone. Some people allow the individual causes to have subcauses, which would be attached to the minor bones. This is intended to get at the fundamental or root causes of the problem. Other people do not include this level of detail on their fishbone diagrams.

When you are done, look at the entire diagram. Does it have reasonable balance across the major bones? Are any common themes emerging? Can you identify causes that are measurable and fixable and which you believe are likely to have a large impact on the problem?

In some situations, you may find that a flow diagram of the work process may be more valuable and informative.

Further reading:

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