Provides a tool for structured brainstorming, which is often more effective than free-form discussion. Fishbone diagrams are also called cause-and-effect (C&E) diagrams or Ishikawa diagrams.

Answers the questions:
  • What are the potential causes for a particular type of defect?
  • What are the process inputs that contribute to variation in the process output?
When to Use Purpose
Pre-project Assist in project identification by linking potential causes to defects.
Start of project Assist in problem identification.
Mid-project Identify potential process inputs to investigate in the project to determine which inputs have a significant influence on the process output.


No data requirements exist because you only use this tool to collect and organize data.


  1. Gather the project team and appropriate stakeholders for a brainstorming session.
  2. Determine the primary categories (affinities) for the causes of the problem (for example, personnel, machines, methods, materials, measurements, and environment).
  3. For each primary category, list all possible causes or process inputs. You may want to establish secondary categories for some or all of the primary categories, then list the causes or process inputs under the secondary categories.
  4. Highlight causes (or inputs) that are deemed to be the most important by the team.
  5. Record the categories and causes, using the fishbone tool.


  • Be sure to include project stakeholders in the brainstorming sessions for building the fishbone diagram.
  • If the standard categories of the causes are not appropriate for the problem, create new ones. For example, service-quality applications often include personnel, procedures, and policies. However, fishbone diagrams can include any type of cause you want to investigate.
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