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Ishikawa diagrams, also known as fishbone diagrams, are a mechanism for generating and mining data to discover the cause and effect of an issue or observation. The technique which was created by Kaoru Ishikawa (1968, University of Tokyo) to show the causes of a specific event. The technique has been adopted and used in many quality and analytical processes such as SAFe’s Inspect and Adapt process. Ishikawa diagrams can also be combined with other techniques such as the “five whys.”

The tools:

  1. Whiteboard/flipchart and dry erase markers

The process for generating an Ishikawa diagram:

  1. Draw a line through the center of the whiteboard or flipchart.
  2. Identify the problem (effect) that will be investigated. Write the problem statement at the far right end of the centerline. A problem statement reflects the issue or idea that is being investigated.
  3. Decide on the major categories of problem’s cause. There are a number of standard categories that vary by industry or problem. For example, the categories that are often used for software projects are people, process, tools, project and environment. There is no hard and fast rules for the number and types of categories; let the problem scenario guide you.
  4. Draw a line for each of categories radiating from the center line. Each line should be at approximately a 60 degree angle from the center line. Distribute the category lines around the center line to approximate the bones extending from a fish spine (hence the name – fishbone diagram).
  5. Brainstorm to identify potential causes of the problem.
  6. Write each cause on a line branching from the related category. Break each cause down into the causes that cause the causes, adding additional branches as needed. Note: a cause can be listed in multiple categories.
  7. As the chart emerges, the facilitator should focus the team’s brainstorming efforts on areas of the chart that have the least detail.
  8. When the team loses focus, the exercise is complete. If the diagraming session is longer than 30 minutes consider taking a break to help keep the team fresh.

The process of generating an Ishikawa diagram focuses a team on defining the causes of a specific effect. The process is often used where identifying potential process improvements is the goal, such as retrospectives. The formality of the Ishikawa diagraming process keeps teams focused on a specific goal.

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