Build an Ishikawa diagram

How to build a fishbone diagram

1. Put the problem in the head. As a fact, as concrete as possible: what goes wrong, how often, for whom. Not the cause and not the solution.
2. Choose the categories. By default the 6 M's: People (Man), Methods, Machines, Materials, Measurements and Environment (Mother nature: place, time, season, culture). Adapt them to your process, and take a moment over it: vague categories lead to debate later about where something belongs.
3. Brainstorm per category. With the people from the process, not on your own. Anything goes on the diagram, judging comes later. Keep asking: "and what causes that?"
4. Pick the key causes. Let everyone put a few marks next to the causes they think contribute most. In the tool that is the star. Those causes go on to the 5 Whys to reach the root cause.

When do you use it?

In the Analyse phase of an improvement project, once the problem is sharp and you want to know where it comes from. The diagram structures the brainstorm and sorts the ideas straight into usable categories. A bonus: the people from the process think along, and so feel ownership of the solution that follows.

Common mistakes

• Writing down solutions as causes. "There should be a checklist" is not a cause. "Steps are skipped because nobody knows them by heart" is.
• Letting only your own department brainstorm. The causes often sit in the chain. Invite the neighbours.
• Stopping at the diagram. A fishbone full of causes is a start. Without choosing and digging deeper it stays a pretty drawing.

More background and a practical example are in the knowledge-base article on the Ishikawa diagram.