3. How do you set up a cause/effect diagram?

The cause/effect diagram should be drawn up as a group. The diagram can be drawn up either immediately after identifying the effect and the problem, or after carrying out a problem analysis and preliminary investigation to identify the majority of the causes of the problem.

In the first case, most of the causes shown on the diagram are only "possible" causes. A field investigation will be necessary to confirm or deny their role in the appearance of the effect, as well as to find the root causes.

In the second case, most of the causes appearing on the diagram will probably be first causes validated during the preliminary investigation. When the diagram is drawn up as a group, it is possible that other possible causes will be identified which had not been considered during the initial investigation; it is only for these "new" possible causes...