October 7, 2020 | Mark Paradies

Fishbone Diagram Root Cause Analysis – Pros & Cons

Pros & Cons of Fishbone Diagram Root Cause Analysis (Ishikawa Diagram)

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 using a Fishbone Diagram. 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 influencing 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), which also includes the video below that outlines the use of 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.

Fishbone Diagram “Pros”

First, let’s review the pros of using Fishbone/Ishikawa Diagrams for root cause analysis.

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.

Fishbone Diagram “Cons”

Now, let’s look at the cons (drawbacks) of using Fishbone/Ishikawa 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…

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 many (or should I say most?) investigators don’t have training in the causes of human errors (the science of human factors). Thus, the bones on their Fishbone Diagrams are their guesses at the causes of human errors, and they don’t have any human factors to guide them beyond their knowledge of human error.

Third, Fishbone Diagrams don’t have any guidance for what a “root cause” is

Many think they know the definition of a root cause but don’t have a standard definition for their team. For an article about defining a root cause, see THIS LINK.

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 selected cause 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. You must understand “What Happened” BEFORE you start trying to find out “Why It Happened.” Without understanding what happened, people using Fishbone Diagrams often jump to conclusions without completing their fact-finding. Thus, they don’t have proof of 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

And these three standard answers certainly aren’t the whole list or an effective list of corrective actions.

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 (and they should), 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 learn 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 website’s picture below to discover the TapRooT® Advantages…

And finally, you can read a white paper that provides an example of how TapRooT® works. Just CLICK HERE to download the PDF.

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. 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.

TapRooT® Implementation Advisors
Quality, Root Cause Analysis
Show Comments

2 Replies to “Fishbone Diagram Root Cause Analysis – Pros & Cons”

  • James Willoughby says:


    “Cause and Effect has several drawbacks…”

    Is the issue more a matter of how certain “cause and effect” methodologies are applied, rather than the notion of “cause and effect” per se. Cause and effect is after all a pretty well-known construct of, well, everything really.

    • Mark Paradies says:

      Cause and effect is a model of reality that we use to make sense of things.

      The problems with cause and effect are problems of how we view things.

      We jump to conclusions. We look for evidence that confirms our beliefs. We have limited knowledge and don’t know all the potential cause and effect combinations.

      These limitations are inherent in humans and cause and effect.

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