My New Book Part 10

Review

In my last post, we continued our discussion on what I believe are the 4 best tools for problem solving.  I discussed the Pareto Chart and presented a simple example of how to construct one.  In today’s post we will look the third tool, the Cause and Effect Diagram.

The 4 Best Tools for Problem Solving (con’t)

The Cause and Effect Diagram

While the run chart answers the questions of if and when a change has occurred and the Pareto chart is more of a comparative tool, the Cause and Effect Diagram is a tool that helps identify, organize, and display possible causes of a specific problem.  The Cause and Effect Diagram, or Fishbone Diagram (because its structure resembles the bones of a fish) is one of the most popular tools ever developed.  It was created and developed by Dr. Kaoru Ishikawa, a noted Japanese consultant, and are also referred to as Ishikawa diagrams in his honor. It graphically illustrates the relationship between a given outcome (the effect) and all the factors that might influence the outcome (the causes).  The structure of the diagram helps the team think in a very systematic way as they look for potential causes of the problem they are trying to solve. Let’s look at a simple example.

 The construction of a cause and effect diagram starts by identifying and defining the outcome or effect being studied (i.e. problem description) and placing it to the far right side of a straight line.  We then establish main causal categories such as man, method, machine and materials and place them at the end of diagonal lines drawn from the central spine of the fish as is illustrated in the figure above.

For each of the main categories, we then identify other, more specific factors that could be the causes of the effect and place them on off-shoot bones from the diagonal lines.  We continue to identify more detailed and more explicit causes and then organize them on bones that come off of the off-shoot bones.

The figure above is a hypothetical cause and effect diagram for a person with diabetes whose blood sugar is out of control.  Four major categories were selected (Food/Nutrition, Medicine, Exercise and Person) and then more specific, potential causes for the out-of-control diabetes were added to each major category.  These more specific secondary causes are seen as the smaller bones on the fish emanating from the major categories at the end of the diagonal lines as we attempt to zero in on our list of potential causes of the problem.  Finally, even more specific causes are added.  For example, under the category Exercise we see that the “level of exercise” is listed with “too low” and “none” completing this series of bones.

In my next post, we complete our discussion on these four important tools by discussing the Causal Chain.  As you go through my postings, if you have any questions for me, send me an email to ras8202@live.com.

Bob Sproull