How to Use the Fishbone Diagrams for Root Cause Analysis-Invensis learning
How to Use the Fishbone Diagrams for Root Cause Analysis-Invensis learning

In the 1960s Kaoru Ishikawa discovered the fishbone diagram. He was a Japanese teacher and a quality management lecturer of his generation. He practiced this tool for the first season when he served with the Kawasaki shipyards in the quality management process. The fishbone diagram is also recognized as the Ishikawa diagram and the Cause and Effect diagram.

What is a Fishbone Diagram?

Fishbone diagram is 1 of the seven quality circles (QC). It serves to reflect the potential causes in line to obtain the root cause of a particular query. It helps to recognize, analyze and fix quality issues. Sometimes, it can also be desirable to analyze what can go wrong – preventing future difficulties. It acquires its name for its appearance shape which matches the side aspect of the skeleton of a fish. 

The “head” of the skeleton represents the difficulty or influence, which is generally shown on the right side. The “bones” extend on the left side to show the various causes. The ribs indicate levels or order of objectives for the analysis, which branch out into causes and sub causes. The branching depends on the standards required under each group.


Drawing a Fishbone Diagram

  • Sketch the head on the right which includes the problem effect or issue for investigation
  • Sketch a decent line from the head, heading to the left. This is the backbone
  • Name the areas, broad level categories, to be thought and branch them from the backbone.
  • Analyze the causes of these categories that contribute to the effect. Combine these elements to the category branches, respectively.
  • Split the causes into sub-causes, till you cannot drill  it down further 

Fishbone Analysis

Fishbone diagrams are practiced in the “Analyze” stage of the DMAIC – define, measure, analyze, improve, and control. It is the method adopted for Lean Six Sigma, a query decoding tool. This diagram is also complemented with why analysis.

The problems in every area are by a drill-down method in the context of the problem (effect). These problems can also be additional, broken into sub-causes for further analysis. Sometimes, it is also described as a Cause-and-Effect diagram, giving attention to the causes. 

Typical practices of the fishbone diagram are to recognize:

– Potential events of problems in new product configuration

– Restriction of quality check

– Possible factors that can cause the error

– Identify the signs of the cause

The method of producing a fishbone diagram can be for both an individual or a company of several people. The first step is to classify the problem. Sometimes the problem can appear to be a symptom too. It is essential to realize that the centre of the Fishbone is not the result, problem or sign, but the beginning of it. Once the query has been obtained out, a brainstorming gathering will take place, independently or in a combination, to find the reasons. The people concerned should come up with all the potential causes of the effect.

A Step-by-step Model to Determine the Causes

1. Classify the problem to be investigated

2. Take up kinds of reasons for analysis. Here, practising the categories of 6Ms, ask the following questions:

  • Man: Any man linked matters to the problem?
  • Machine: What are the machine-related doubts?
  • Method: What is wrong in the process connected that is giving the appearance to the difficulty?
  • Measurement: Any tool or regular mistake that requires rectification?
  • Material: What turns in the parts of the matter that happened?
  • Environment: What was environmental fitness?

3. Dig down more, by suggesting “Why” to the first level of causes.

4. Note these cases on the major sections.

After all, the potential and possible causes have been identified; these causes must be rated. The rating is prepared based on the impact of the object on the effect. The evaluation will decide the value and criticality of the cause and shall be worked upon. The brainstorming gathering will continue to rate various reasons. Based on the most critical rating, the solutions will be offered.

Critical care to be taken:

  • The problem should be apparent.
  • There should be no uncertainties concerning the issue.
  • The person or the team member who are working to identify the causes should be encountered. This prevents from missing out the essential purposes of the difficulty. 
  • The brainstorming assembly should be adjusted and goal-oriented. All potential causes should be known. Only after all the causes are identified, they are considered. If the bones grow, the accuracy of the fishbone diagram must not be missed. 

Brainstorming and Fishbone – Who Should Utilize this Tool?

The most relevant question about Fishbone is who is operating to implement it. The issue occurs when organizational thinkers sit on choosing a complicated organizational difficulty. People who could brainstorm with real solutions are the ones to be included.

Those are IT personnel, engineers, people who are technically healthy and have organizational information should be given this task to implement. Such people would have all territories to recognize an organizational dilemma with its root. Their judgment would matter among leadership to identify the root cause, the non-conformance. Once the root cause is identified, a course is automatically set to determine the organizational difficulty.


It is an essential tool in classifying the root cause, though its construction is time-consuming. Owing to its tremendous advantages, the fishbone diagram is applied across different enterprises like manufacturing, project administration, service manufacturers, etc.

The advantage of the fishbone diagram depends on how the diagram is generated. The skill level, knowledge, analytical thinking, education, etc. of the person or people involved playing a significant role in the flourishing drafting of the fishbone diagram. It is essential to include experienced specialists to draft the fishbone diagram and request many as “whys” to obtain the root cause. 

To learn more about fishbone diagrams and other methods for root cause analysis and prevention, one should take part in widely-recognized quality management certification courses from an accredited training provider.   

Some of the popular quality management certification courses that individuals and enterprise teams can take up are:

Lean Six Sigma Green Belt Certification Training

Lean Six Sigma Black Belt Certification Training

Lean Six Sigma Yellow Belt Certification Training

Lean Fundamentals Training

RCA through Six Sigma Training

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Diego Rodriguez works as a Six Sigma Black Belt professional for a leading manufacturing company. He possesses ample experience in various aspects of quality management, such as Lean, Six Sigma, Root Cause Analysis, Design Thinking, and more. His primary focus is to conduct tests and monitor the production phase and also responsible for sorting out the items that fail to meet the quality standards. Diego’s extensive work in the field has resulted in being an honorary member of quality associations globally. His areas of research include knowledge management, quality control, process design, strategic planning, and organizational performance improvement.


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