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  • Writer's pictureJoe Mlynek, CSP, OHST

Root Cause Analysis And A Fishbone?

Updated: Apr 27

One of my latest blogs discussed the Five Why approach to incident analysis. While this approach provides an easy to use tool for minor incident or those with less potential, it does have limitations. This blog discusses the Fishbone Process. This method was initially developed to identify quality issues but can be applied to just about any problem or incident. Let’s walk through the steps of the process.

Draw a Fishbone Diagram

On a whiteboard or flipchart, draw the skeletal system of a fish. Start with the head and the backbone. The head represents the problem, and the backbone represents the causal factors that contribute to the problem.

Fishbone diagram for root cause analysis

Define the Problem

The problem, or head of the fish, may include incidents involving property damage, environmental impacts, injury, or near miss events. As mentioned earlier this approach may also be used to address quality issues such as bottlenecks, lead time concerns, etc.

Identify Causal Factors of the Problem

The causal factors of the problem form the rib bones attached to the fish’s backbone. There are six rib bones, or causal factors, that could contribute to the problem. The six causal factors are referred to as the ”Six M’s”:

  • Man (People)

  • Machine (equipment)

  • Mother Nature (environment)

  • Materials (raw materials)

  • Methods (process)

  • Management (leadership/decision making)

For each of the Six M’s ask, “why does this happen or what could happen?” The answers comprise what are called sub-bones (sub-causes). The sub bones are attached to each of the six major bones of the skeletal system.

Identify Potential Root Causes

Once the sub bones (sub-causes) are identified, analyze each of them and decide on those that have the strongest effect on the problem. These sub bones (sub-causes) become the “root cause(s).”

Fishbone Safety Offers More

The Fishbone offers a more thorough approach to root cause analysis. This approach will require an investment of time. Solid investments provide greater returns. I think you will find this true of the Fishbone Process.


Joe Mlynek is a partner and subject matter expert at Safety Made Simple, Inc. He has over 20 years of experience in safety at the corporate level and as a consultant. He is a Certified Safety Professional (CSP) and Occupational Safety and Health Technician (OHST). Joe can be reached at

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