Tree diagram (probability theory)

Tree diagram for events $A$ and $B$.

In probability theory, a tree diagram may be used to visualize a probability space. Each node on the diagram represents an event and is associated with the probability of that event. The root node represents the entire probability space and therefore has probability 1. A set of sibling nodes represent an exclusive and exhaustive partition of the parent event.

Probabilities associated with branches represent probabilities conditional on the parent event.