Fishbone Diagram

A fishbone diagram is a problem-solving tool to analyze possible causes of a problem.

There are often are multiple reasons a problem occurs. Consequently, it can be challenging or intimidating to tackle complex problems. Therefore, it’s important to first breakdown a problem into smaller more manageable problems. By breaking a problem into smaller components it is easier to see important details that otherwise go unnoticed. Finally, it is easier to infer cause-and-effect relationships when looking at smaller pieces rather than observing an entire system.

The dimensions commonly analyzed in a fishbone diagram are:

  • Man — causes related to the people doing or managing the job
  • Method — causes related to how the job is done, including the tools used
  • Machine — causes related to equipment used in the process
  • Material — causes related to parts used in the process
  • Environment — causes related to the condition of the area where the job is done

Fishbone Diagram Example

A fishbone diagram breaking down a service problem (5% of our customers receive the wrong order) across man, machine, method, material, and environment.

When building a fishbone team members should be careful to include only the actual physical causes. It can be tempting to include items someone believes is happening or wishes were happening. Consequently, a fishbone can turn into a “wishbone” diagram.

Types of Root Cause Analysis

There are three types of causal analysis:

  1. Logic
  2. One-variable-at-a-time statistical analysis (OVAT)
  3. Multiple-variables-at-a-time statistical analysis (MVAT)

Logic-based analysis includes tools such as the fishbone diagram, fault trees, and 5 why, among others.

A chart showing the types of causal analysis - logic, OVAT, and MVAT - across two dimensions: complexity of analysis and time to resolve. The fishbone diagram is a logic method.

Teams can solve most problems through qualitative logic and critical thinking. Organizations should not jump to advanced mathematical tools. Firstly, these complex methods are likely inappropriate for most problems. Secondly, the tools can alienate team members unfamiliar with them. As a result, it can discourage them from contributing to improvement.

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