The Fishbone Diagram. How does it work?

The Fishbone Diagram is a Brainstorming based technique explained in depth in our Quality Fundamentals Unit Business Performance Improvement. Its value is that it enables the orderly clustering of possible causes of a problem into groups whilst the brainstorming process is taking place. and links ideas that possibly have some interactive relationship. Without the Fishbone diagram or something like it, such clustering could take considerable time where standard brainstorming or post it stickers were used instead to identify the theoretical causes.

Sadly, the technique is widely misunderstood both in the way it is constructed and in its use.

If it is constructed correctly, it is not unusual for it to display some 50 or so possible causes.  The converse is also true.   If it only contains a few possible causes say less than 10 the probability is that frequently but not always, the diagram was not constructed correctly.

The most common mistake that is made using the Fishbone Diagram is to make the assumption that the most popular possible cause must be the real culprit.   This is especially the case when either the group are being pressed to solve the problem or when the real cause seems obvious.  Invariably this will result in significant under achievement.

The reason is that for there to be just one actual cause of most problems is relatively rare. In most cases there are multiple causes each of which may on occasions be the outstanding culprit.  Of these it does not always follow that the most popular cause is actually the most important. Invariably it is not. In many cases, when subsequent data is collected, there have been some big surprises. Never make assumptions, they are often wrong.

The consequence of not being careful is that when a falsely selected 'major' cause is eliminated, the problem might well occur less frequently but it will still occur.  So, further investigation is necessary and if the team are to be successful they will have to collect and analyse data.

Typically, this also uses the basic problem solving tools, the most popular in this instance being the Check Sheet and its companion the Pareto Diagram.  Sometimes the 'tally check' technique proves useful. If these simple tools are used correctly, experience shows that the most incredible results can be achieved both quickly, and easily.

There is a lot more detail that we could have gone into here but this would require more than a Blog. The entire Problem solving process is included in the DHI e-learning programme Quality Fundamentals where the student is taken through the entire problem solving process using a series of animation videos.   If a group is formed to view this material, the materials are designed to encourage the students to tackle a live project of their own choosing from their work and should reach a positive conclusion whilst they are working.

Please check this out on and in particular Unit 4 of the 5 Unit course Quality Fundamentals.