Fishbone diagram

The Fishbone diagram is named for its resemblance to a fishbone with the investigated problem being in the place of the head and the identified root causes coming out of the spine (see picture). It is also called an Ishikawa diagram after its creator Kaoru Ishikawa or a Cause-and-Effect diagram. Identifying the root causes of a problem makes it a valuable tool in Risk Management, as it can help the team figuring out how best to handle this with ARTA.

This article will focus on the fishbone diagram. It will consider how the diagram is appropriately used in Risk Management as well as its purpose ans limitations. It will also touch upon tools that can be used in conjunction with the diagram to strengthen a project's management of risks. The article will be based on previous literature on the subject.

The Purpose of the Fishbone Diagram

The purpose of the fishbone diagram in Risk Management is to identify various root causes of a potential problem for a project or program. It does so by having the user brainstorm over various causes for the problem and continuously going to deeper levels by finding the cause of the previous cause. Thus a cause-rib might have more subcauses, see the Illustration. The process of making new "ribs" on the fish continues until the team agrees, that the root cause has been reached. In this way the tool aims at organising the causes for the investigated problem. But the team does not have to find deeper levels for each cause they identify, only for those that they deem are "Very Likely" or "Somewhat Likely" to happen and will be "Very Easy" or "Somewhat Easy" to control or fix (see "Application" step 4 for reading more about these gradings). The reason for this is so that the team does not waste time and effort on treating a cause that is unlikely to happen or that they won't be able to do anything about anyway. If the team is hard pressed for time and have a lot of causes to look into, they can start with the ones they deem will have the highest impact or effect in causing the problem.

Application of the Fishbone Diagram

When a team is doing risk management they will often need several fishbone diagrams as each one only corresponds to one problem while several problems may arise during a project. A problem could, as suggested earlier be something like the risk of customers not buying a car. Thus the problems are the risks the team will want to manage. It is also called an effect which is how the diagram also got the name Cause-and-Effect diagram. When using the fishbone diagram it is particularly useful to do so on a large surface -such as e.g. a whiteboard, with lots of space for categories, subcategories, and causes, since the team cannot know at the beginning of the process just how many of these will be needed. Following is a step by step guide to using the fishbone diagram