Fishbone Diagram

Fishbone diagrams, also known as Cause & Effect diagrams, organize possible causes into an easily understood format.

A fishbone diagram exercise is very useful for

  • organizing input from multiple individuals
  • documenting investigation priorities
  • noting which causes are ruled in and out in the Analyze phase

Completing a Fishbone Diagram

(see the Downloads tab if you need a template)

Plan the Meeting

  • Fishbone diagrams are best completed in a team setting, where those most knowledgable about the problem-at-hand get together and combine their thoughts to complete the diagram.
  • Plan the meeting at least one week in advance, and clearly communicate the meeting objective.
  • An example of a meeting objective might be:  ”Complete a fishbone diagram for motor life cycle failures are experiencing, and agree on top causes / actions to investigate.”

Meeting Flow

  • At the start of the meeting, show a fishbone diagram example, review the meeting objective, and ask for any questions on the definition/scope of the problem to be discussed.
  • If you are solving a manufacturing problem, it is helpful to review the “6 M’s” that the potential causes will likely fall into:  Manpower, Methods, Machines, Metrics, Materials, and Minutes (time).
  • Let the team know that no idea is considered irrelevant – all potential causes will be noted, and then the team will prioritize which causes to go after first.
  • Go around the room and ask team members what they think the potential contributors of the problem could be, write the ideas on small pieces of paper (sticky notes are ideal), and stick them on the wall or large dry-erase board.
  • Keep the meeting moving and avoid discussing any one cause for too long.
  • Once all of potential causes have been listed, group the them under major headings like the 6 M’s above .  It’s okay not to have the headings decided upon at the start of the meeting.  Sometimes it’s best to identify the group headings once the potential causes are listed.
  • Each group heading will represent a bone on the fish (reference the introduction page), and then the individual causes can be listed along each bone.

Success comes down to good facilitation and getting the right people in the session – design experts for product issues, process experts for process issues, oftentimes each of these combined provides the magical combination needed to solve the problem.  Get the people who know the process and or product intimately.

The next time you are faced with a complex problem involving many potential solutions, consider using a fishbone diagram to bring the team together and organize potential causes.

For more fishbone diagram examples and templates, see fishbonediagram.org.

Good luck in your process improvement endeavors!

Here is a fishbone diagram for a quality issue in a power tool assembly plant.

Specifically, a cordless drill line was failing in the field (high warranty rate) due to drills “clutch-out in drill mode,” i.e. the drill clutch was slipping when holes were being drilled (clutching is only supposed to take place when driving screws).

Fishbone (cause and effect) diagram for clutch failures

Fishbone diagram for clutch failures.

In the above case, the team grouped possible causes into the three categories noted on the diagram (Assembly, Design, Purchased Components).

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