Ishikawa diagram
Ishikawa diagram: a fishbone-shaped cause-and-effect diagram that sorts the possible causes of a quality or cost problem into branches such as materials, methods, machines and people.
FrameworkTotal quality management (TQM)
See it move
A moulding workshop's Ishikawa diagram sorts the causes behind 200 defective units, 8% of a 2,500-unit batch, into four branches: Materials, a new resin supplier; Machine, a mould run 40,000 cycles since calibration; Method, a changed cooling-time setting; and People, a new night-shift operator. Tracing each defect back found 150 of the 200, three-quarters, came from the worn mould.
Check yourself
A logistics firm draws an Ishikawa diagram to investigate late deliveries, with branches for Materials (packaging), Methods (routing software), Machines (delivery vans) and People (driver training). Of 300 late deliveries logged last month, 210 were traced to the Methods branch, 60 to Machines, 20 to People, and 10 to Materials. Based on this breakdown, which branch should the firm prioritise for corrective action, and what share of late deliveries does it account for?