Fishbone diagram
A fishbone diagram, also called an Ishikawa or cause-and-effect diagram, maps the possible causes of a problem by sorting them into categories that branch off a central spine, with the problem written at the head. It structures root-cause analysis.
How it works
The problem statement goes in a box at the right, the fish's head, with a horizontal arrow as the spine. Major cause categories branch off as bones; common sets are people, methods, machines, materials, measurement and environment, or for services, policies, procedures, people and place. The team brainstorms specific causes under each category and asks "why?" repeatedly to add deeper causes as smaller bones.
The diagram was developed by Kaoru Ishikawa, a pioneer of quality management in Japan, and is one of the seven basic quality tools. When the group runs out of ideas, ASQ advises looking harder at the categories with the fewest causes, then choosing which causes to investigate further.
A worked example
Complaints about lost bags are up 30 percent at an airline, and its customer team writes that problem at the head of a fishbone. The diagram lists 17 possible causes across 6 categories. Interviews with 25 affected travelers and staff narrow them to 2: a new connection time at one hub and tags printed on a failing printer at another.
Related
Automate this in Pulse
Each bone of a fishbone diagram can be checked against Pulse's themes from customers who hit the problem, marking which suspected causes customers actually describe.