The fishbone diagram, developed by Dr. Kaoru Ishikawa, is a powerful quality tool used to analyze and understand the root causes of a problem. It helps teams systematically explore various factors that may be contributing to an issue. Here’s how it works:
Problem Statement (Effect): Start by defining the problem or effect you want to investigate. Write it at the center of the diagram.
Major Categories (Causes): Brainstorm and identify major categories of potential causes related to the problem. Common categories include:
Methods
Machines (equipment)
People (manpower)
Materials
Measurement
Environment
Branches and Sub-Causes: Create branches extending from the main arrow, representing each major category. Then, brainstorm all possible causes within each category. Ask “Why does this happen?” repeatedly to dig deeper and identify sub-causes.
Causal Relationships: Layers of branches indicate causal relationships. Some causes may appear in multiple places if they relate to several categories.
Thorough Thinking: Continue asking “Why?” and generating deeper levels of causes until the team exhausts ideas. Focus on areas where ideas are scarce.
Visual Representation: The resulting diagram resembles a fishbone, with the problem statement at the head and branches representing causes.
The fishbone diagram helps teams organize their thinking, encourages collaboration, and provides a structured approach to problem-solving. It is particularly useful during brainstorming sessions and root cause analysis1.
References:
The ASQ Certified Manager of Quality/Organizational Excellence Handbook, Fifth Edition. Sandra L. Furterer and Douglas C. Wood. ASQ Quality Press, 20212.
ASQ Quality Tools - Fishbone Diagram3.
Quality Nugget: Creating Ishikawa (Fishbone) Diagrams With R (Software Quality Professional)1.
