The Fishbone Diagram
The Fishbone diagram was originally developed by Professor Kaoru Ishikawa, a Japanese quality control statistician, as a quality management processes in the Kawasaki shipyards. He developed the diagram to assist teams in categorizing the many potential causes of problems in order to identify root causes.
How to Construct:
- Place the main problem under investigation in a box on the right.
- Draw four to six bones off the spine. These will be your process variables. Place them into naturally related groups. The labels of these groups are the names for the major bones on the Ishikawa diagram.
- Combine each bone in turn, ensuring that the process variables are specific, measurable, and controllable. If they are not, branch or “explode” the process variables until the ends of the branches are specific, measurable, and controllable.
- Take care to identify causes rather than symptoms.
- Post diagrams to stimulate thinking and get input from other staff. Sources of variation can be rearranged to reflect appropriate categories with minimal rework.
- Ensure that the ideas placed on the Ishikawa diagram are process variables, not specially caused other problems such as tampering, etc.
- Review the quick fixes and rephrase them, if possible, so that they are process variables.
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