Fishbone Diagram

What is this technique about

A fishbone diagram is a visual tool used to identify the root causes of a problem. The method is a more structured approach to other root cause identification tools such as 5 Whys. The problem or the effect is displayed on the head of the fish (as shown in the figure below), and the possible causes are listed along the smaller bones of the fish under various categories. It is also possible to create nested causes.

A Fishbone diagram is a structured method for identifying the causes of a specific problem. The tool may be used to

1. 1. Identify the root causes of a problem
   2. Categorise causes and understand the relationship between causes

Where does it come from 

The Fishbone diagram or the Ishikawa diagram was developed by professor Kaoru Ishikawa, a pioneer in quality management In 1960’s and was published in his book “Introduction to Quality Control” In 1990.

For which purposes it is used (why in your engineering teaching)

The Fishbone diagram can be used in the beginning of creative processes of the engineering design process, i.e., the initial problem analysis. The method is ideal to analyse the root cause of a problem, and activate structured thinking and reasoning process.

How to use it

1. 1. Identify the problem by creating a clear problem statement. (example of a problem. “students having lower attention span in class”). The problem/effect is written on the head of the fish  (see the figure for reference).
   2. Brainstorm the major categories of the causes of the problem. A facilitator should manage the conversation and to document the causes mentioned during the brainstorming session. The categories of the causes can be customised according to specific needs. However, the categories generally include:
      
      1. 1. Methods
         2. Machines
         3. Materials
         4. Measurement
         5. People
         6. Environment
   3. The causes may be written down along the smaller bones based on the categories. If required, it is possible to mention the causes in multiple categories and create branches within the causes (as shown in the figure). Layers of branches indicate causal relationships.
   4. Using the listed causes and inferred causal relationships, identify the root causes of the problem and prioritise them. Prioritising the root causes is important if the activity is required to create solutions later . This process of prioritising the root causes can be further subdivided as follows:
      
      1. 1. Each of the team members and the facilitator is allocated a specific number of votes (say 5 and represented by a “✔”). The number of votes alloted to each of the Identified cause (as observed from the fishbone diagram), indicates the criticality of the cause. Higher the number of votes, higher is the critical nature of the cause.
         2. The team members and facilitator allocate their votes to one or more identified causes in the fishbone diagram (but limited to a total of pre-agreed limit, in this case 5).
         3. Based on the total count of votes against each of the identified causes (as observed in the fishbone diagram), the identified root causes can be prioritised for generating solutions.