October 7, 2020 | Mark Paradies

Fishbone Diagram Root Cause Analysis – Pros & Cons

Pros & Cons of Fishbone Diagram Root Cause Analysis

Recently, I’ve seen several articles explaining Fishbone Diagram root cause analysis. They explain how they use the technique but they usually leave out the disadvantages of Fishbone Diagram root cause analysis. Therefore, I thought I would outline the pros and cons of Fishbone Diagram root cause analysis.

How Fishbone Diagram Root Cause Analysis Works

The root cause analysis technique called a Fishbone Diagram (or an Ishikawa Diagram) was created by university professor Kaoru Ishikawa in the 1960s as a quality control tool. He published a description of the technique in 1990 in the book, Introduction to Quality Control.

book about Fishbone Diagrams

A Fishbone Diagram (a sample of which is shown below) shows the problem at the head of the fish-like looking diagram and a backbone with major factors that can bring success or failure to the process as the major bones attached to the backbone. In the example below the major factors are:

  • Site
  • Task
  • People
  • Equipment
  • Control

Fishbone Diagram 1

Each of the major factors then has additional bones attached to that category that outline the cause and effect relationship that may be causing the problem.

You can use many techniques to develop a cause and effect relationship, but people often describe using a 5-Why type questioning process to create the cause and effect bone structure.

Another method that people use to develop the bone-like structure is brainstorming. The team brainstorms the major factors that influence performance (the main bones attached to the backbone). Then they brainstorm potential root causes of the problem for each major performance factor. The team then reviews their potential causes and identifies the “most likely” root cause (or, in some cases, root causes).

The diagram above comes from this article (LINK) that also includes the video below that outlines using a Fishbone Diagram.

Another article used the example below to describe a Fishbone Diagram…


fishbone Diagram 2


Now that you understand what a Fishbone Diagram looks like and how you might draw one, let’s review the pros and cons of the technique when it is used for root cause analysis.

Pros of Fishbone Diagram Root Cause Analysis

First, let’s review the pros of a Fishbone Diagram.

Let’s start with the fact that a Fishbone Diagram is fairly easy to use. Like 5-Whys and Brainstorming (which can be used to develop the “bones”) the technique is simple to learn and apply.

Next, the technique is visual. It is easy to see what the investigator sees as the main problem (the head of the fish), the major factors influencing performance (the main bones attached to the spine), and the potential causes (the minor bones). the Fishbone Diagram provides a relatively easy to understand diagram of the cause and effect relationship that the investigator wants to communicate.

Also, Fishbone Diagrams have a long history of over 50 years of use. It certainly was one of the original techniques developed to help problem solvers understand the causes of a problem.

Finally, many claim that it is an effective root cause analysis tool.

Cons of Fishbone Diagram Root Cause Analysis

Now, let’s look at the cons (drawbacks) of using Fishbone Diagrams for root cause analysis.

First, the technique is based on the root cause analysis technique of cause and effect. Cause and Effect has several drawbacks that we have documented in previous articles. For example, these three articles outline many of the drawbacks of Cause and Effect analysis…

“Fast” Root Cause Analysis: Brainstorming, 5-Whys and Fishbone Diagrams

Problems using 5-Whys? Read “Under Scrutiny” from Quality Progress to understand why!

Are You Dissatisfied with 5-Whys Root Cause Analysis?

Second, in all the examples I’ve seen, there is no guidance for building the bones of the fish. The building of the bone structure depends on the knowledge of the investigator or investigative team. And, as described by Barb Carr in the article below, many (Or should I say most?) investigators don’t have training in the causes of human errors (the science of human factors). Thus their bones on their Fishbone Diagrams are their guesses.

Root Cause Analysis Tip: An ASQ discussion on Quality, Root Cause Tree, and the Ishikawa diagram (also called fishbone diagrams or cause-and-effect diagrams)

Third, Fishbone Diagrams don’t have any guidance for what is a “root cause.” Many think they know the definition of a root cause but don’t have a standard definition for their team. For an article about the definition of a root cause, see…

Definition of a Root Cause

Fourth, the other technique that can be used to develop the bones of a Fishbone Diagram – Brainstorming – has all the same drawbacks already mentioned.

Fifth, I’ve heard people use “voting” by the team as a way to determine the “root cause” of the many bones on the Fishbone Diagram. Brainstorming followed by voting is simply the team’s opinion. It doesn’t prove that the cause that was selected caused the incident (problem).

Sixth, Fishbone Diagrams don’t help the investigator determine what happened, which really should be explored before one starts trying to figure out why the incident/problem happened. Thus, people using a Fishbone Diagram to find root causes often jump to conclusions without completing their fact-finding. Thus, they don’t have proof to show why the bones on their Fishbone Diagram are root causes.

Seventh, Fishbone Diagrams provide no guidance to help investigators develop effective corrective actions. Therefore, the team often ends up picking one or more of the three standard corrective actions:

  • Training
  • Procedures
  • Discipline

The seven “cons” mentioned above are serious drawbacks to performing a thorough, fact-based root cause analysis and developing effective fixes.

If these drawbacks concern you, you might consider another root cause analysis tool.

TapRooT® Root Cause Analysis

TapRooT® Root Cause Analysis is a systematic, guided process for investigating incidents (problems) and developing effective fixes to prevent repeat failures.

Here are three ways to find out more about how TapRooT® Root Cause Analysis can help you improve performance.

First, you can watch this video of Mark Paradies, one of the co-creators of the TapRooT® System, being interviewed on Worldwide Business by Kathy Ireland…

Second, click on the picture of the website below to discover the TapRooT® Advantages…

And finally, you can request a white paper that provides an example of how TapRooT® works by filling out the brief information requested below…

TapRooT® Root Cause Analysis Training and Software

If you would like more information about TapRooT® Training, see THIS LINK.

If you would like more information about TapRooT® Software, see THIS LINK.

Thanks for reading this article about Fishbone Diagram root cause analysis, and if you would like to talk about your root cause analysis needs, please call one of our experts at 865-539-2139 or contact us by using THIS LINK.

Quality, Root Cause Analysis
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