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 this event. The root node represents the entire probability space and therefore has probability 1. Its child nodes represent a set of events partitioning the whole space. Further branches represent partitions of the respective parents, and so on.

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