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Previous: Ishikawa Fishbone Diagram

The cause-and-effect diagram, also called a “Fishbone diagram” or "Ishikawa Fishbone Diagram" because of its appearance, allows you to map out a list of factors thought to affect a problem or desired outcome.  It is an effective tool for analyzing processes and situations and for planning.  The “Fishbone Diagram” is essentially a pictorial display of a list that demonstrates the relationship between some “effect” and all the possible "causes” influencing it.  The effort or problem is stated on the one side of the fishbone diagram, and the major causes are listed to the other side .

For every effect, there are likely to be several major categories of causes.  The major causes generally can be summarized under five categories:  Equipment; Methods; People; Materials; Environment.  In administrative areas, it may be more helpful to use these categories:  Policies Procedures; People, and Plant.  You may choose any categories that make sense to you or help you to think creatively.  The Ishikawa fishbone diagram is a great group brainstorming process.
 

To create a Fishbone diagram:

1.      Identify a problem you need to analyze and ask a group of 5-6 people who are affected 
         by or can provide input into the problem to help you analyze the causes.

2.      Generate the causes needed to build the Fishbone diagram  in one of the two ways:

  a.    Conduct a structured brainstorming session with the group about possible causes
    without previous preparation                              

   b.    Ask members of the group to spend time before the meeting to take notes for several
     days about things they see as probable causes to the problem.          

3.      Construct the actual Fishbone diagram:

   a.    Draw a large horizontal arrow and place the problem statement in a box to the right
     of the arrow.  This becomes the spine of the Fishbone diagram;

   b.    Next draw the “bones” (causes) off the spine and label them with the major category
     headings that you’ve chosen such as equipment, methods, people, materials,
     environment, etc.

   c.    Place the brainstormed ideas in the appropriate major categories.

   d.    For each cause ask, “Why does it happen?” and list responses as branches off the
     major causes.

4.      Interpret the Fishbone diagram. In order to find the most basic causes of the problem.

   a.    Look for causes that appear repeatedly;

   b.    Look for trends where one category of cause has many smaller bones coming off it;

   c.    Get the group to agree where the most likely cause is occurring;

   d.    Gather data to determine the relative frequencies of the different causes.

From this well-defined list of possible causes, the most likely are identified and selected for further analysis.  When examining each cause look for things that have changed, deviations from the norm or patterns.  Remember, look to cure and not at the symptoms of the problem.