Fish Bone Diagram-Root-Cause Analysis technique
What is Fishbone Diagram
A fishbone diagram is one of the analysis techniques or approaches to problems. Using the technique analysts can find the root causes of the problem i.e. why the issue or defect or problem occurs. It helps to identify and analyze the issue and its root causes.
The fish-bone diagram is also known as Ishikawa diagram and the Cause-and-Effect diagram.
Karou Ishikawa proposed this fishbone approach at the University of Tokyo in 1943 and hence it is referred to as Ishikawa diagram.
Components of Fishbone Diagram
The fishbone diagram looks like a fishbone structure or fish skeleton. The diagram looks like below.
- Problem Statement
The head of fish represents the problem.
2. Categories of causes
The categories of causes of the problem are the bones of fish at the left and right side of the spine (middle bone).
3. Factors
The factors or sub-causes lie under corresponding categories are represented by horizontal lines attached to the bones.
To identify the factor under each cause category, you need to ask the ‘Why’ question. I.e. why the cause, what are the reasons that fall into the category.
Example of Fishbone Diagram
To learn the application of fishbone diagrams, let us consider the below example.
The problem statement is “Poor Quality Product.”
Categories for Causes are considered as below.
- Processes
- Manpower
- Tools
- Budget
To identify the causes and factors of a problem, expertise is required. Critical thinking and knowledge must be applied to the problem to identify the major and all other factors.
Advantages of Fishbone Diagram
- It is easy to understand the problem and its root causes.
- The diagram is easy to understand.
- The fishbone approach can be applied to different industries.
- Once all causes have been identified, analysts can take relevant actions to improve the problem or processes.
- Various Different causes come into the picture at once.
Disadvantages of Fishbone diagram
- The diagram does not differentiate the major and minor defects based on their severity.
- Brainstorming requires identifying all causes-category and sub-causes or factors.
