Cause and effect diagram (CED)

It is an easy yet powerful graphical tool used for identifying the causes of a problem or effects. It helps to define and analyze the root causes that affect a process which leads to a certain problem.

This diagram was developed by Kaoru Ishikawa, a famous Japanese consultant in 1950. Hence, it is also known as the Ishikawa diagram.

It is also known as the fishbone diagram because the completed graphic resembles the bone of a fish. It is most useful when the team approach is used to identify a problem. In a team, there are different opinions to the root cause of the problem. This diagram helps to capture the different opinions and stimulates brainstorming on the root causes of the problem. It helps the team to organize the causes behind the problem into categories and helps them not only to proceed systematically but also helps them to reach a common understanding of a complex problem.    

It is important to understand that the various tools in Six Sigma don’t work in isolation; rather, they are dependent on each other in some ways.

The use of this diagram is not restricted to one particular industry; it has a wide and varied area of application. It finds its application in manufacturing, marketing, sales, and administration departments. It also finds its use in research, innovation, engineering and project management, and many more.

The video goes on to explain the construction of the Cause and Effect Diagram in easy steps 

The problem statement or the opportunity that we are trying to improve forms the head of the fishbone. A straight horizontal line is drawn from the head, the ‘bones’ coming off this line represent the various categories of the causes of the problem. Often the causes are categorized under people, equipment, materials, external factors, etc. Many times, the 6Ms are used as the categories for the bones when determining the root cause of a problem in the manufacturing industry and 4Ps in the Service Industry.  However, these categories are not restricted only to the ones mentioned above, and they can also be modified or interchanged according to a particular situation. The team members can delve deeper into the problem to reach the root cause of the problem by applying the 5 Whys.

Ultimately the tool helps to determine the root causes of the problem in the process which enables us to improve upon those causes to reach the desired outcome and improve the process.