Fishbone Diagram (Ishikawa)

What it is and when to use it

When something goes wrong, the fastest explanation people reach for is usually “someone made a mistake” — and that's rarely the whole story. A fishbone diagram forces a structured look across every category that could be causing the effect (method, machine, material, people, measurement, environment) before anyone commits to a fix. It's a hypothesis map, not a verdict — each branch still needs to be checked against real data before you spend money acting on it.

What goes on the sheet

1. The effect/problem statement, defined precisely (what, where, when, how much)
2. Six cause categories: Method, Machine, Material, Manpower (people), Measurement, Environment — or the four adapted for service work: Policies, Procedures, People, Plant/Place
3. Candidate causes listed under each category, from a group session, not one person's opinion
4. For each candidate cause, whether it's verified against real data or still a hypothesis
5. The 2-3 causes selected for deeper analysis (feeds directly into 5 Whys or a Pareto)
6. Date and team who built it, so it can be revisited instead of redone from scratch

In a business like yours

• Online shop: late orders checked against six possible causes before anyone buys a new printer.
• Restaurant: long ticket times sorted into people, equipment, method, supplies, measurement and layout.
• Roofing crew: repeat leaks after install broken down cause by cause, with evidence for each.

Illustrative examples, not client cases.