Cause & Effect Diagram

The cause & effect diagram is the brainchild of Kaoru Ishikawa, who pioneered quality management processes in the Kawasaki shipyards, and in the process became one of the founding fathers of modern management. The cause and effect diagram is used to explore all the potential or real causes (or inputs) that result in a single effect (or output). Causes are arranged according to their level of importance or detail, resulting in a depiction of relationships and hierarchy of events. This can help you search for root causes, identify areas where there may be problems, and compare the relative importance of different causes.
Causes in a cause & effect diagram are frequently arranged into four major categories. While these categories can be anything, you will often see:

• manpower, methods, materials, and machinery (recommended for manufacturing)
• equipment, policies, procedures, and people (recommended for administration and service).

These guidelines can be helpful but should not be used if they limit the diagram or are inappropriate. The categories you use should suit your needs. At SkyMark, we often create the branches of the cause and effect tree from the titles of the affinity sets in a preceding affinity diagram.
The C&E diagram is also known as the fishbone diagram because it was drawn to resemble the skeleton of a fish, with the main causal categories drawn as "bones" attached to the spine of the fish, as shown below.

How to use it:

Before constructing the Cause-and-Effect Diagram, you need to analyze the causes. The steps are as follows:

1. Re-examine the problem by asking:
   • What is the problem?
   • Who is affected?
   • When does it occur?
   • Where does it occur?
     
2. Brainstorm the team's ideas about the causes of a problem using the Causal Table or "Why-Because" Technique.
   
3. The list of causes should be grouped by relationships or common factors using an affinity technique.
4. You can now illustrate graphically the causes grouped by relationships by using a Cause-and-Effect Diagram where:
   
   
   • The problem under investigation is described in a box at the head of the diagram.
   • A long spine with an arrow pointing towards the head forms the backbone of the "fish." The direction of the arrow indicates that the items that feed into the spine might cause the problem described in the head.
     
   • A few large bones feed into the spine. These large bones represent the main categories of potential causes of the problem. Again, the arrows represent the direction of the action; the items on the larger bones are thought to cause the problem in the head.
     
   • The smaller bones represent deeper causes of the larger bones they are attached to. Each bone is a link in a Cause-and-Effect chain that leads from the deepest causes to the targeted problem. 
   
   
   
   
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1.Cause and effect tool that helps identify , sort and display possible causes of a problem or quality characterstics.

2. Please note that it is NOT used to identify the root cause. Only data can do that.

Benefits of using cause and effect diagram

1.Helps determine possible cause
2.Encourages group participation
3.Uses an orderly , easy to read format
4.Indicate possible cause of variation
5.Increase process knowledge
6.Identify areas for collecting data