Fishbone / Ishikawa Diagram
The fishbone diagram structures all plausible causes of a problem into categories (the 6 Ms), so the team thinks across the whole breadth before drilling into the depth — and no cause family is overlooked.
A precise, measurable problem statement (the fish’s head) — agreed before the meeting
A cross-functional group: operator, technician, quality, planning as relevant
Data about the problem is in the room: when, where, how often
The problem in the head to the right, six bones: Man, Machine, Method, Material, Measurement, Milieu. In administrative processes, replace as needed (e.g. System, Information, Procedure). The categories are scaffolding — not dogma.
All plausible causes on sticky notes, placed on the relevant bone. No discussion of right/wrong yet — criticism at this stage locks out the quiet participants’ knowledge, and they are often the ones who know.
For the heaviest causes: why does it arise? Sub-causes are drawn as side bones. The diagram may well become messy — it is a way of thinking, not a presentation.
Which causes are supported by data (when/where patterns)? Which can be quickly checked at the gemba? Choose the 2-4 most likely for verification. A vote without data chooses the best-phrased cause — not the right one.
Each selected cause is tested: can it turn the problem on/off? Do measurements support it? The confirmed causes are carried into 5 Whys to root cause and countermeasure.
How it goes wrong in practice — and this is where most implementations part ways.
A neat fishbone is a collection of hypotheses. Without the verification step, nothing is found — only proposed.
“Inattention”, “carelessness”, “lack of motivation” are not causes — they are symptoms of system causes (unclear standard, poor layout, time pressure). Drill further.
“Poor quality” gives a fishbone the size of a whale and just as manageable. Narrow down: one defect type, one area, one period.
The method only works when it becomes daily routines and leadership behaviour. The operations check shows in 4 minutes where your operations stand — and what should come first.