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Cause and Effect Diagrams also called Fishbone diagram is a process improvement technique that enables taking action on the causes of variation. In practical applications, the number of possible causes of variation for any given problem can be of different varieties. The fishbone diagram was developed by Dr. Kaoru Ishikawa as a simple method of graphically displaying the causes of any given quality problem. They are tools that are used to organize and graphically display all of the knowledge associated with a problem. It represents the result of the brainstorming exercise a group has relating to a particular problem.

Types of Cause and Effect Diagrams

The following are two types of cause and effect diagram:

  • The dispersion analysis type: This can be created by repeatedly asking “why does this dispersion occur?”
  • The production process class: This type uses production processes as the main categories, or branches, of the diagram.

Implementing Cause and Effect Analysis

The following are some steps for implementing cause and effect analysis:

  1. Development of a flow chart of the area to be improved.
  2. Definition of the problem to be solved.
  3. Brainstorming to find all possible causes of the problem.
  4. Organizing the brainstorming results in rational categories.
  5. Constructing a cause and effect diagram that accurately displays the relationships of all the data in each category.

Constructing the Fishbone Diagram

Constructing the cause and effect diagram is very simple, and it involves the following steps:

  1. Construct a box on the far right-hand side of a large sheet of paper and draw a horizontal arrow that points to the box. Inside of the box, write the description of the problem you are trying to solve.
  2. Write the names of the categories above and below the horizontal line. Think of these as branches from the main trunk of the tree.
  3. Draw in the detailed cause data for each category. Think of these as limbs and twigs on the branches.

A good cause and effect diagram should have many “twigs”. A fishbone diagram having a lot of smaller branches indicates show thorough understanding of the problem.

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