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The Fishbone Diagram

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The fishbone diagram or Ishikawa diagram is a cause-and-effect tool that helps identify reasons for imperfections, variations, defects, or failures.


The diagram looks just like a fish’s skeleton with the problem at its head and the causes for the problem feeding into the spine. Once all the causes that underlie the problem have been identified, managers can start looking for solutions to ensure that the problem doesn’t become a recurring one.


This tool can also be used in product development. Having a product which solves user problem(s) can help ensure that your new development will be popular – provided people care about the problem you’re trying to solve. The fishbone diagram can serve to identify the weaknesses with current market offerings so that you can develop an innovation that doesn’t have these problems.


The fishbone diagram is also a great way to find the cause of current or potential quality problems.


How to use the Fish Bone Diagram

  • Agree on the problem statement (also known as the effect). Write this at the mouth of the “fish.” Be as clear and specific about the problem. Beware of defining the problem in terms of a solution (e.g., we need more of something).

  • Agree on the major categories of causes of the problem (branches from the main arrow). Major categories often include: equipment or supply factors, environmental factors, rules/policy/procedure factors, and people/staff factors.

  • Brainstorm all the possible causes of the problem. Ask “Why does this happen?” Capture the causal factor as a branch from the appropriate category on the fishbone diagram. Causes can be written in several places if they relate to several categories.

  • Again asks “Why does this happen?” about each cause. Write sub-causes branching off the cause branches

  • Continue to ask “Why?” and generate deeper levels of causes and continue organizing them under related causes or categories. This will help you to identify and then address root causes to prevent future problems.


Note: Using the Five Whys is a great way to generate potential.

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