The Fishbone Diagram

What is the Fishbone Diagram?

The fishbone diagram was developed in the 1940s by the Japanese Kaoru Ishikawa, who is considered the pioneer of quality management in Japan. The method is one of the seven basic quality tools (Q7).

The Ishikawa or Fishbone diagram is used to visualize a problem solving process. It is primarily used to search for the cause of the problem. The diagram can be used in the context of a Six Sigma project at any stage of the project when the causes of existing problems need to be found and ideas for solutions evaluated. The goal is to determine all possible causes of a problem and to identify the primary trigger, so that a reliable starting point for further planning is available. By using the Ishikawa Diagram a graphical representation of the problem should be possible as well as the possible causes should be shown. The result is a prioritized list of possible causes and a list of measures to be taken to solve the problem.

Advantages of the Fishbone Diagram

The great strength of the Fishbone diagram is that it brings together a wide range of information from participants with different expertise. The problem and its causes are systematically separated from each other so that the participants focus on the causes and background. First of all, all possible causes are identified so that no rash measures are taken that may not be efficient or even harmful. The development of the diagram in an interdisciplinary team leads to a multifaceted approach. The gradual structuring from main to secondary causes helps to find the actual cause




Risks and Limits

The Ishikawa diagram itself is only used to identify the causes of problems. Effects and solutions of the problem must be worked out in separate steps. In addition, the given main influencing factors can restrict the free thinking of some participants. If the process is not well moderated, there is a risk of paying too much attention to unimportant causes. In addition, there is the risk of identifying only superficial causes if the participant does not have sufficient expertise to identify the actual trigger of the problem.

Steps to create the Fishbone Diagram

  1. Problem Formulation
    Although the problem is already known before the method is performed, first take the time to formulate the problem accurately and completely. If necessary, discuss when the problem occurs, under what conditions, and who is involved. Then name the problem briefly and concisely. Write it down on a sheet of paper on the right – the “head” of the fish
  2. Naming the most important influencing factors
    Before the team begins to search for concrete problem causes, identify possible main influencing factors and place them as main branches (or “fishbones”). With enough categories, the environment of a problem is completely described, thus ensuring that as many causes as possible are collected.
  3. Checking completeness You will probably never know whether all possible causes have been found. But a final check and control of all categories is useful.
  4. Evaluate and select causes From this step on, things usually become really productive: the most probable causes are selected from the many collected causes. This step is often not so easy. Especially when a lot of causes have been collected. In a discussion, there is quickly the danger of getting bogged down. A very nice variant works as follows: Ask your participants to mark their most probable causes with a red dot or other markings. For example, each participant receives three points, and several points can be assigned to one cause.
  5. Derive actions In the last step, the selected causes are checked for correctness and the measures and next steps are derived

15 thoughts on “The Fishbone Diagram”

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