11.1 Sample spaces and probability rules

Ideas in this lesson

Equally likely outcomes

Count favorable outcomes within a finite sample space whose elementary outcomes are equally likely.

Complements

The probability of an event not occurring is one minus the probability it occurs.

Unions and intersections

For a union, add the two event probabilities and subtract their overlap once.

Mutually exclusive events

Disjoint events have no shared outcomes; their intersection has probability zero.