What are Fishbone Diagrams?

The fishbone diagram, also called the Ishikawa diagram, was created in Japan. The story goes that fishbone diagrams were first used in engineering the Mazda sports car. These kinds of diagrams have since become popular in many parts of the modern business world, including in manufacturing, where they can be useful in assessing what has gone wrong with a complex process.

Fishbone diagrams are composed of a main horizontal line where smaller lines branch off of the main line diagonally. This makes the chart look like a fish skeleton. The “fish bones” represent cause and effect in a situation where it’s necessary to troubleshoot a production problem or other dilemma. The fishbone diagram provides a much better “quick picture” perspective than a block of text, which is a main part of its appeal to busy executives.

Fishbone diagrams for product design, quality control, and other common uses often group different types of causal factors onto the same fish bone or category. These include people, or those who are involved in the process, as well as Method, or how the job was designed to be done. Other categories include Machines, the gear used in the process, Materials, the raw goods used, and Environment, a larger catch-all term for a variety of causal factors. Some types of fishbone diagrams use words with the same beginning letter to promote easy categorization.

Fishbone diagrams could be called an “aggregate model” since they incorporate smaller causes contributing to larger ones. This is represented by small diagonals attaching to the various diagonals that attach directly to the main horizontal line. This kind of model is useful in visually assessing a number of conditions or events that may have a bearing on a production outcome.

Fishbone diagrams are just one of several types of cause and effect diagrams that planners can use to minimize problems in a task. The same kinds of professionals who use fishbone diagrams may use histograms, pareto charts, scatter diagrams, control graphs, check sheets, or any number of other planning and troubleshooting tools. In more complex systems involving money or other variables, advanced planning might utilize tools that measure or quantify a variable condition in more abstract ways. Computers have made more kinds of projections in decision-making possible for human planners, and in the modern world of planning, fishbone diagrams represent a more concrete or basic planning tool.