Fishbone (Cause-Effect / Ishikawa) Diagram

A fishbone diagram, also called a cause and effect diagram or Ishikawa diagram, is a visualization tool for categorizing the potential causes of a problem in order to identify its root causes. Typically used for root cause analysis, a fishbone diagram combines the practice of brainstorming with a type of mind map template.

A fishbone diagram is useful in product development and troubleshooting processes to focus conversation. After the group has brainstormed all the possible causes for a problem, the facilitator helps the group to rate the potential causes according to their level of importance and diagram a hierarchy. The design of the diagram looks much like a skeleton of a fish. Fishbone diagrams are typically worked right to left, with each large “bone” of the fish branching out to include smaller bones containing more detail.

Dr. Kaoru Ishikawa, a Japanese quality control expert, is credited with inventing the fishbone diagram to help employees avoid solutions that merely address the symptoms of a much larger problem. Fishbone diagrams are considered one of the seven basic quality tools and are used in the “analyze” phase of Six Sigma’s DMAIC (define, measure, analyze, improve, control) approach to problem solving.

How to create a fishbone diagram
Fishbone diagrams are typically made during a team meeting and drawn on a flipchart or whiteboard. Once a problem that needs to be studied further is identified, teams can take the following steps to create the diagram:

The head of the fish is created by listing the problem in a statement format and drawing a box around it. A horizontal arrow is then drawn across the page with an arrow pointing to the head, this acts as the backbone of the fish.
Then at least four overarching “causes” are identified that might contribute to the problem. Some generic categories to start with may include methods, skills, equipment, people, materials, environment or measurements. These causes are then drawn to branch off from the spine with arrows, making the first bones of the fish.
For each overarching cause, team members should brainstorm any supporting information that may contribute to it. This typically involves some sort of questioning method, such as the 5 Whys or the 4P’s (Policies, Procedures, People and Plant) to keep the conversation focused. These contributing factors are written down to branch off their corresponding cause.
This process of breaking down each cause is continued until the root causes to the problem have been identified. The team then analyzes the diagram until an outcome and next steps are agreed upon.

When to use a fishbone diagram
A few reasons a team might want to consider using a fishbone diagram are:
To identify the possible causes of a problem.
To help develop a product that addresses issues within current market offerings.
To reveal bottlenecks or areas of weakness in a business process.
To avoid reoccurring issues or employee burnout.
To ensure that any corrective actions put into place will resolve the issue.

Author = Margaret Rouse (WhatIs.com)

https://whatis.techtarget.com/definition/fishbone-diagram

This cause analysis tool is considered one of the seven basic quality tools. The fishbone diagram identifies many possible causes for an effect or problem. It can be used to structure a brainstorming session. It immediately sorts ideas into useful categories.

WHEN TO USE A FISHBONE DIAGRAM
When identifying possible causes for a problem
When a team’s thinking tends to fall into ruts

FISHBONE DIAGRAM PROCEDURE
Materials needed: marking pens and flipchart or whiteboard.
Agree on a problem statement (effect). Write it at the center right of the flipchart or whiteboard. Draw a box around it and draw a horizontal arrow running to it.
Brainstorm the major categories of causes of the problem. If this is difficult use generic headings:
Methods
Machines (equipment)
People (manpower)
Materials
Measurement
Environment
Write the categories of causes as branches from the main arrow.
Brainstorm all the possible causes of the problem. Ask “Why does this happen?” As each idea is given, the facilitator writes it as a branch from the appropriate category. Causes can be written in several places if they relate to several categories.
Again ask “Why does this happen?” about each cause. Write sub-causes branching off the causes. Continue to ask “Why?” and generate deeper levels of causes. Layers of branches indicate causal relationships.
When the group runs out of ideas, focus attention to places on the chart where ideas are few.

Author = ASQ

https://asq.org/quality-resources/fishbone

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