Cause and Effect Diagram, also known as a Fishbone Diagram or an Ishikawa Diagram, is a process analysis tool used to explore potential sources of variation in a process and graphically display the relationship between a specific problem or effect and its potential causes. Using a Cause and Effect Diagram helps the problem solving team be systematic in generating and grouping the various assumptions about the causes of the problem under investigation. Cause and Effect Diagram allows the team to carry out investigation beyond the symptoms of the problem, prevents the team from jumping to solutions prematurely, identifies multiple causes that contribute to the problem or effect, and provides useful information for various process improvement initiatives. The long horizontal arrow on the Cause and Effect Diagram points to the problem or effect. The branches or arrows off the long horizontal arrow represent major categories of causes and each category may have several subcategories. The major categories of causes traditionally include methods, equipment, materials and people; however, depending on the type of processes and specific problems under investigation the major categories of causes may vary significantly. Another variation of the Cause and Effect Diagram is to use key process steps as the major categories and identify the causes of the problem at each step of the process. The figure below illustrates customized variation of the Cause and Effect Diagram.
