What is a cause-and-effect diagram and when is it used?

A cause-and-effect diagram, also called a fishbone diagram or Ishikawa diagram, is a quality tool that visually maps all potential causes of a problem or defect. The problem is placed at the head of the fish, and major cause categories form the bones, typically organized as manpower, methods, machines, materials, measurements, and environment. Sub-causes branch off each major category. The team brainstorms possible causes and plots them on the diagram to identify root causes rather than symptoms.