Also known as Fishbone Diagram, Ishikawa Diagram, Herringbone Diagram, and Fishikawa Diagram.

When you have a serious problem, it's important to explore all of the things that could cause it, before you start to think about a solution. That way you can solve the problem completely, first time round, rather than just addressing part of it and having the problem run on and on. Cause and Effect Analysis gives you a useful way of doing this. This diagram-based technique pushes you to consider all possible causes of a problem, rather than just the ones that are most obvious.

Follow these steps to solve a problem with Cause and Effect Analysis:

Identify the problem

First, write down the exact problem you face. Where appropriate, identify who is involved, what the problem is, and when and where it occurs.

Then, write the problem in a box on the left-hand side of a large sheet of paper, and draw a line across the paper horizontally from the box. This arrangement, looking like the head and spine of a fish, gives you space to develop ideas.

Example:

In this simple example, a manager is having problems with an uncooperative branch office.

Figure 1 – Cause and Effect Analysis Example Step 1

Figure 1 – Cause and Effect Analysis Example Step 1

Some people prefer to write the problem on the right-hand side of the piece of paper, and develop ideas in the space to the left. Use whichever approach you feel most comfortable with.

It's important to define your problem correctly. Look at the problem from the perspective of customers, actors in the process, the transformation process, the overall world view, the process owner, and environmental constraints.

By considering all of these, you can develop a comprehensive understanding of the problem.

Work out the major factors involved

Next, identify the factors that may be part of the problem. These may be systems, equipment, materials, external forces, people involved with the problem, and so on.

Try to draw out as many of these as possible. As a starting point, you can use models such as strategy, structure, systems, shared values, skills, style and staff as factors that you can consider or product, place, price, and promotion as possible factors.

Brainstorm any other factors that may affect the situation.

Then draw a line off the "spine" of the diagram for each factor, and label each line.

Example:

The manager identifies the following factors, and adds these to his diagram:

  • Site
  • Task
  • People
  • Equipment
  • Control
Figure 2 – Cause and Effect Analysis Example Step 2

Figure 2 – Cause and Effect Analysis Example Step 2

Identify possible causes

Now, for each of the factors you considered in step 2, brainstorm possible causes of the problem that may be related to the factor.

Show these possible causes as shorter lines coming off the "bones" of the diagram. Where a cause is large or complex, then it may be best to break it down into sub-causes. Show these as lines coming off each cause line.

Example:

For each of the factors identified in step 2, the team brainstorms possible causes of the problem, and adds these to the diagram, as shown in figure 3.

Figure 3 – Cause and Effect Analysis Example Step 3

Figure 3 – Cause and Effect Analysis Example Step 3

Analyse your diagram

By this stage you should have a diagram showing all of the possible causes of the problem that you can think of.

Depending on the complexity and importance of the problem, you can now investigate the most likely causes further. This may involve setting up investigations, carrying out surveys, and so on. These will be designed to test which of these possible causes is actually contributing to the problem.

A useful way to use this technique with a team is to write all of the possible causes of the problem down on sticky notes. You can then group similar ones together on the diagram.