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The What, Where, and How of Fishbone Analysis

A fishbone analysis, also known as a cause and effect diagram or an Ishikawa diagram, helps teams analyze multiple potential causes of a detrimental effect. The diagram gets its name from the way the causes and effects are visualized, with the problem at the fish’s head, and causes along the spine like ribs. 

The fishbone diagram, a type of root cause analysis, was popularized in the 1960s by Kaoru Ishikawa, a University of Tokyo professor who focused on quality strategy in post-war Japan. Fishbone diagrams are often referred to as Ishikawa diagrams for this reason. This type of root cause analysis is useful in situations where there are many potential causes of a single problem. This makes it ideal for large, multidisciplinary teams working together to identify causes and solutions. Because the technique is fairly easy to use, it’s also helpful for teams untrained in more technical root cause analysis methodologies. 

How to Use Fishbone Analysis

For a fishbone diagram to be productive, a team must first isolate the problem it needs to solve. A clearly defined effect is placed at the “head” of the diagram, and a spine is drawn straight out from the head. Then, general categories of causes must be added, branching off either side of the spine like ribs. These categories are likely unique to your specific problem. However, if you struggle to identify broad umbrellas under which potential causes will fall, you can start with categories based on Six Sigma’s six Ms. In this case, your diagram will have “ribs” labeled:

  • Procedures
  • People
  • Machines
  • Materials
  • Measurements
  • Environment

Brainstorm specific potential causes under each of these categories, as well as any tailored to your industry or problem. Continue to drill down by repeatedly asking, “Why?” You’ll uncover causes that were not immediately obvious using this method. Document each new cause as it’s identified using “bones” jutting from your diagram’s ribs. Some causes may belong to multiple categories. After exhausting the team’s ideas, you can prioritize which causes will be explored as potential solutions to the initial problem. This can be done with the group as a whole or within specialty-based teams.

Where to Use Fishbone Analysis

Fishbone diagrams are an incredibly useful root cause analysis tool in many industries and situations. In manufacturing, they are used for quality control (as described by Professor Ishikawa) and continuous improvement. Fishbone analysis can also be used when designing new products. In this application, the team would identify all causes contributing to a problem with current products in order to create a product without these negative effects.

The fishbone diagram is also beneficial for healthcare providers working in hospitals, nursing homes, private practices, etc. These organizations can use the methodology to enhance the overall quality of care by improving patient communication, prioritizing training, and preventing slips and falls.