Fishbone diagrams, also known as cause-and-effect diagrams, are about organizing possible causes behind a given problem. Of course, all possibilities will need to be proved or disproved during the Analyze phase of the project.
The following Fishbone Diagram example looks at possible causes of employee turnover, based on an excellent article from Sigma Assessment Systems, Inc.
Constructing a Fishbone Diagram
Visit fishbonediagram.org for a thorough review of fishbone diagrams and Excel/PPT templates.