How to use a Fishbone Diagram?
Kaoru Ishikawa invented the fishbone diagram in the 1960s. He was a Japanese professor and a quality management innovator of his time. He used this tool for the first time when he worked with the Kawasaki shipyards in the quality management process. The fishbone diagram is also known as the Ishikawa diagram, as a tribute to its creator.
What is a fishbone diagram?
A fish-bone diagram is one of the seven quality circles (QC) tools. It helps to visualize the potential causes in order to find the root cause of a particular problem. It helps to identify, analyze and improve quality issues. Sometimes, it can also be helpful to analyze what can go wrong - preventing future problems. It derives its name for its shape which resembles the side view of the skeleton of a fish.
The "head" of the skeleton depicts the problem or effect, which is usually shown on the right. The "bones" extend on the left to show the different causes. The ribs denote categories or classification of causes for the analysis, which branch out into causes and sub causes. The branching depends on the levels required under each classification.
The company Toyota popularized a classification concept of 6 Ms. Sometimes it includes Management and Maintenance along with the categories mentioned below. The 6 general categories of analysis are:
6. Mother Nature/ Milieu (Environment)
- Some marketing industries use the categories as 7Ps:
And some Service industries use the 5Ss:
Drawing a fishbone diagram
- Draw the head on the right which contains the problem (effect or issue) for analysis
- Draw a straight line from the head, leading to the left. This is the backbone
- Identify the areas, broad level categories, to be studied and branch them from the backbone.
- Analyze the causes from these categories that contribute to the effect. Connect these causes to the category branches respectively.
- Break down the causes into sub-causes, till you cannot drill down further causes.
The process of creating a fish-bone diagram can be for either an individual or a team of several people. The first step is to identify the problem. Sometimes the problem can seem to be a symptom too. It is important to understand that the heart of the fishbone is not the effect, problem or symptom, but the cause of it. Once the problem has been found out, a brainstorming session will take place, individually or in a group, to find the causes. The people involved should come up with all the possible causes of the effect.
A step-by-step guide to find the causes:
Example 1: XYZ Manufacturing Pvt. Ltd.
One important point to note is that the categories mentioned are only to give a sense of direction. All problems may not have caused by each of these categories. The categories can be changed depending on the problem or industry.
Example 2: ABC Pvt. Ltd
A company, ABC Pvt. Ltd. identified that their sales of a particular Product A fell by 36% in June this year. The company decided to find the root cause of fishbone analysis. This is the diagram that was projected.