Fishbone Diagrams – Otherwise Known as the Cause and Effect Diagram or Ishikawa Diagram

The Japanese are well known for their huge contributions to the process of improving production and quality management. One of such contributions is the introduction of the Fishbone Diagram by Kaoru Ishikawa in the 1960s. That came about while he was working towards implementing quality management processes in the Kawasaki Shipyards.

The Fishbone Diagrams are used by quality managers to show the causes of certain events. They are so called because once drawn, they look very much like the shape of a fishbone; with the causes form the branches of the bone and the effect (problems or events) taking the place of the head. For example, let’s say an organisation has a problem of one or more products turning out with defects every time. This is an event which could be costing them plenty of money as time goes on. Hence, to solve the problem, the product quality managers have to identify the causes of the problem.

Now, instead of just writing long notes that may become too difficult to read, it’s usually best if the causes are placed in the branches of the Fishbone Diagram while the problem, i.e. defects in products, are placed at the peak or head of the bone structure. This way, anyone can just pick up the diagram and understand the causes of the problem and the problem itself.

How to Construct a Fishbone Diagram:

So how exactly do you construct a fishbone diagram? This should already be obvious from the illustrations above but, just in case it isn’t yet, here is a more in depth explanation.

To construct a fishbone diagram, it is usually best to start by identifying the problems. And a good way to do so is to start by asking questions. For instance, if the problem is related to products been returned by customers, you’d want to ask questions such as: “Why are they been returned?” and “what are the causes of the defects”. Asking these questions will help while brainstorming for the causes of the problem.

Once the main cause of the problem has been discovered, the next thing you and your team might want to do is to draw a horizontal line and place the main problem in a box joined with the tip of the line - on the right hand side. Then, each potential cause of the problem, as identified earlier, should be placed in individual boxes (on both sides of the initial line drawn) and connected to the main horizontal line by slightly angled lines. After inputting every single cause alongside the problem, you’d discover you have a complete fishbone diagram.

Now that you have drawn up a fishbone diagram, it should be relatively easy to move towards eliminating the problems. Since it is likely that you’ll be doing this in a team, the diagram can be more effective if you take the time to seek everyone’s opinion throughout the process. Also, you’d take the fishbone diagram task further by prioritising each causes of the problem. This way, you and your team will know which ones to tackle first and which to handle last.