Fish diagram

Kaoru Ishikawa, Professor of Tokyo University, he published the assumptions of his chart in 1962. The purpose of this method is to identify causes of incurred or potential failures. For this reason, it is also known as a cause and effect chart, and due to the distinctive look - fish chart. The scope of application of this method was initially limited to industry, but in a short time, it has proven to be useful in many other areas. It can by successfully used in services, public administration, project management.

The preparation of the chart must be effort of many employees in the organization, because the causes of failures usually have their sources in various fields of operation. That's why the team should consist of people with high expertise, who, in addition, have a willingness to disclose the causes of defects, also those caused by themselves. Heuristic methods prove to be useful when creating Ishikawa chart.

Design

Chart consists of the arrows along with descriptions, merging in such a way that the main arrow indicates the final effect, which is usually a description of the failure.

Categories of causes usually are selected from a set of:

• man,
• machine,
• material,
• method,
• management,
• environment,

in accordance with the principle of 5M + E. It is also possible to use other categories (e.g. procedures, equipment, information, people) depending on the area in which the chart is used. Each category is developed through indication of causes. If necessary, also secondary causes can be shown. Expansion of the chart ends at the moment the full identification of the causes of the phenomenon.

Advantages and disadvantages

Advantages of using a fishbone diagram include:

• Identifying the root cause of a problem
• Encouraging team participation and brainstorming
• Identifying a large number of possible causes in a short amount of time
• Illustrating the relationship between cause and effect
• Being a simple and easy-to-understand tool

Disadvantages of using a fishbone diagram include:

• Over-simplifying complex issues
• Focusing on immediate causes rather than root causes
• The potential for groupthink and lack of dissenting opinions
• Limited ability to prioritize causes or show the relative importance of different causes.

Fish diagram — recommended articles

Failure Mode and Effects Analysis — Kaoru Ishikawa — 5 whys — Brainstorming — Frank Bunker Gilbreth — Affinity diagram — Quality circles — FMEA analysis — 7 quality tools

References

• Ishikawa Chart on ASQ