The QA SysOp begins the root cause analysis by creating a rough outline of a causal tree on the Blank Causal Tree form, which is then used and refined throughout the investigation process.

The rough causal tree provides a map for the investigator to follow in developing the questions necessary to explore all the antecedent events.

The tree in progress also serves as a helpful communication tool when explaining the event, particularly to someone who was not directly involved but who can assist in identifying contributing factors.