Cause and Effect (Fishbone) Diagram - How to Use This Diagnostic Tool

Sep 12, 2026

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The Cause and Effect (Fishbone) Diagram is a diagnostic method that helps teams identify, sort, and visually display possible causes behind a problem or desired outcome. It supports exploring primary and secondary causes, clarifying how they connect, and building shared understanding through structured discussion. The diagram enables quality improvement by facilitating brainstorming of testable causes and potential solutions, and it guides users to apply reflective review and follow-up planning.

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Cause and Effect (Fishbone) Diagram

What it is and how it helps

How to use the tool

After filling out the diagram

References

Cause and Effect (Fishbone) Diagram What is it and how can it help me? This diagnostic tool—also known as a fishbone diagram—helps teams identify, sort, and visually display all possible causes of a problem or outcome. A cause and effect diagram: 􀂃 Guides teams in exploring the primary and secondary causes of a complex problem 􀂃 Shows how these various causes are interrelated 􀂃 Sparks conversation and builds shared understanding about these causes 􀂃 Supports quality improvement by giving teams an opportunity to brainstorm possible solutions to these causes How to use this tool: 􀂃 Box 1: Identify the main problem that you and your team wish to solve or improve upon. Record the problem in the box labeled 1 (which represents the head of the fish) . 􀂃 Box 2: Discuss the potential primary causes of the problem as a team. Some typical categories of primary causes are people, processes, policies/environment, technology/materials, and systems. Record the primary causes of the problem in the boxes labeled 2 (which represent the spines of the fish) . 􀂃 Line 3: Further discuss the secondary causes of the problem—in other words, the specifics of how each primary cause contributes to the problem. Record these secondary causes under each corresponding primary cause on the lines labeled 3 (which represent the bones of the fish). 􀂃 Line 4: Continue to explore these secondary causes by asking “Why?” until you have identified a cause that is specific enough that you can test a change to it and measure its effect. (For more guidance, refer to The Five Whys Worksheet.) Record any additional causes of the problem under each corresponding secondary cause on the lines labeled 4. After filling out this tool: 􀂃 Reflect on the completed diagram, which now shows all potential causes affecting your complex problem. 􀂃 Discuss whether your understanding of the problem has changed and, if so, how. 􀂃 Identify potential solutions to address the causes of the problem. (For more guidance, refer to the Agreement and Certainty Matrix.) References: 1. Ishikawa K,石川馨. (1986) Asian Productivity Organization. Guide to Quality Control. 2. The Fundamentals of Cause and effect (aka Fishbone) Diagrams. (n.d.) . Retrieved April 24, 2018, from [https://www.isixsigma.com/resource-pages/the-fundamentals-of-cause-and-effect-aka-fishbone-diagrams/](https://www.isixsigma.com/resource-pages/the-fundamentals-of-cause-and-effect-aka-fishbone-diagrams/)

FAQs

What is the Cause and Effect (Fishbone) Diagram used for?

It helps teams identify, organize, and visualize possible causes of a problem or outcome so they can better understand what drives it.

How do you fill out the main parts of the fishbone diagram?

Record the main problem in Box 1, list primary causes in the spines (Box 2), add secondary causes under each primary cause on the lines labeled 3, and then use the “Why?” prompts on lines labeled 4 to reach testable causes.

What should teams do after completing the diagram?

Teams should reflect on the full set of potential causes, discuss whether their understanding changed, and identify solutions to address the causes, supported by related decision tools.

Sep 12, 2026

Upload by Mimi