Root Cause Analysis Tool: Cause and Effect Diagram

July 12, 2010 at 8:05 pm Leave a comment

Root Cause: Fishbone

OK, this is another installment in the series of blogs that are focused learning a systematic, repeatable m sustainable approach to quality improvement. If you think about the series so far we are still in the planning stage of the PDCA cycle or Stage A in the PI CME process. Hang in there we are about to get to the part we all love – proposing, planning and implementing solutions. This is another tool we can use to get at the root causes of a problem.

A Fishbone Diagram aka Ishikawa Diagram aka Cause and effect Diagram is one of the seven basic tools of quality. A caution – use of the tool assumes that a problem has been clearly identified and there is agreement on the definition of the problem. Without that clarity it will be difficult to an agreement on possible causes of the concern. The term Fishbone is used to describe this tool because it actually resembles the skeleton of a fish with a head, spine and bones. It is an effective tool to use in identifying and organizing possible causes – not the symptoms – of a problem. It is not used to analyze data to verify the cause of a problem but rather to help organize your ideas about the causes of a problem.

So how do you develop a “Cause and Effect” diagram?

  • First, the problem you are concerned about is place in a box representing the head of the fish. Remember there has to be agreement on the definition of the problem.
  • A long line with an arrow is drawn pointing to the head. It is along this line that additional lines with arrows are drawn at an angle pointing to the spine representing what might be a significant cause of the problem – people, materials, equipment, policies, procedures, methods – whatever you think is appropriate for the issue of concern. These are the bones of the fish. The few large bones feed into the fish should represent the potential main causes of the problem.
  • Smaller bones are drawn off of the spine bones representing deeper causes of the larger issue to which they are attached. Each bone should be linked in a cause and effect relationship that leads to a deep understanding of the targeted problem.

Make sure each bone, regardless of where it is in the diagram, shows a cause and effect relationship. A helpful way to approach this is to use what you learned in the “Five Whys” tool. Each major spine is the first answer to a “why” question. Answers to the subsequent “why” questions are placed n that spine and lead to that deeper understanding of the problem you are looking for before committing resources to verifying the causes and proposing solutions.

This sounds like a laborious process but it really isn’t. A few brainstorming sessions with the people involved in the process under examination can develop a very descriptive picture of the potential causes and effects of an issue that everyone can agree on.


Entry filed under: Improvement, PI CME, Uncategorized. Tags: , , , , .

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