1.4 Complements, Intersections and Unions

Complements

Venn diagrams can be a useful way of visualising a sample space. Below we can see which equally-likely outcomes of the roll of a die are square numbers, and which are not.

The event not square, or square, is called the complement of square. For any event \(A\):

\[P(\text{not }A)=P(\bar{A})=1-P(A)\]

Intersections