What is a Fishbone diagram

The fishbone diagram or Ishikawa diagram (named after Dr. Kaoru Ishikawa ) is a diagram that resembles a fishbone, or rather a fish skeleton that is viewed from the side. The main purpose of the fishbone diagram is to show what will cause a specific event. What will be caused relates to both primary and secondary causes for a specific event, so the diagram can help all eventualities be considered.

History Of The Fishbone Diagram

The first fishbone diagrams were used by the Japanese quality ‘guru’ in the 1960’s. Soon it was established as one of the most fundamental tools to be used in quality management and it is as widely used today as it used to be in the 1960’s.

How a Ishikawa Diagram Works

The diagram works by an event being placed on the ‘backbone’ of the fish and then lines from there, show the primary causes and secondary causes.

So to analyse a basic problem such as ‘no electricity’ the problem would be highlighted on the backbone and all primary and secondary causes will be identified.

No electricity could be caused by not paying the bill, by the utility company being inefficient, by building works that are being undertaken etc.

Once completed it provides a pictorial assessment of our problem and potential route causes.

Fishbone diagrams as brainstorming tools

The fishbone diagram forces you to think along logical lines, in other words, to take an issue and think about it until you have thought about every single result that could happen.

The process of thinking about something to the ‘nth’ degree can be helpful because it sorts out the relationship between cause and effect and helps all those involved understand that each action or event has a consequence i.e you look at the causes and they drive a certain event to happen. Fishbone diagrams are great when coupled with 5 why analysis.

Groups Of Causes

Sometimes there are certain ‘groups’ of causes that help focus those involved in the brainstorming session to focus on certain different issues. So you may have a list that looks at people, methods, machinery and materials etc. This will help to focus attention on the highlighted groups. For example, when thinking about people you would consider staff, customers, competitors, suppliers etc and think about how a certain event could have been caused by people.

The joy of this diagram is that through thinking about a certain event, it is easier to see all the possible implications that actions may have and in this way there are no ‘unforeseen’ actions that will arise from being unaware, all potential problems have been identified and given due consideration.

Use Of The Fishbone Diagram

The fishbone diagram has a number of applications, but it can be particularly useful when it is applied to trying to rectify faulty goods or poor levels of service because it helps people to first identify and then analyse the potential causes for the problem. This can be a great facilitator in improvement programs.

For example, traditionally after an issue of faulty goods has been raised, then just one reason for this occurrence is sought and once the reason has been identified then action is taken in one area. But if the fishbone diagram is used, then all the potential causes or reasons for faulty goods are identified and then management can ensure that they take the appropriate steps to ensure that they are all eradicated.

Thus the fishbone diagram is a very useful tool when it comes to quality management and because it is usually done in a group setting as part of a brainstorming session, it becomes a means of empowering people to input into the quality process and helps staff to feel involved and as if they are being listened to.