Saturday, December 21, 2013

Fishbone diagram

The fishbone diagram:

The fishbone diagram is one of the easiest mind mapping / problem solving tools available.  It is so simple and straightforward that anyone with the knowledge about a certain topic can generate a diagram to show its cause / effect conditions.  Below is a generic representation of a fishbone diagram.

In illustrating a problem root cause analysis, a diagram as above can be generated.  During its generation, ideas must be poured out without much thought or evaluation yet.  Start from the effect (PROB) which is the "head" of the fishbone, and then proceed to ask why-why questions so as to generate ideas for possible root causes.  A probable cause must be evaluated for further probable causes.  So based on the above, there are four major possible root causes, A, B, C, and D.  Each of them have their own possible root causes as well.  the yellow color boxes are examples of root causes as they are the ones without further identifiable causes (thus, root).  Each root cause can appear in one or more instance.

After generating the fishbone, an evaluation of the probable root causes must be designed by experimentation so as to rule out the non-contributing causes.  A simple table is normally generated to summarize the results.  An example is shown below:


With this exercise therefore, we are able to determine that the root cause of the problem is "M" and therefore, correcting this root cause will solve our problem under study.

For better results, a team approach to this discipline is a good option.  More minds can lead to a wider fishbone and thus can capture more possible root causes.  As the saying goes, "more heads are better than one."