# What Are Mutually Exclusive Events?

## What Are Mutually Exclusive Events?

Two or more events are mutually exclusive if they cannot happen at the same time.

## A Real Example of Mutually Exclusive Events

It is easier to understand mutually exclusive events with an example.

### Tossing a Coin

A tossed coin can either land as **Heads** or as **Tails**. It cannot land as both at the same time.

**Heads** and **Tails** are mutually exclusive events.

## Exhaustive Events

A set of events are *exhaustive* if they include all possible outcomes.

**Heads** and **Tails** are exhaustive events because they are all the possible outcomes of tossing a coin.

### Probabilities of Exhaustive Events Sum to 1

If a set of mutually exlusive events are exhaustive, their probabilities add up to 1.

If a coin is tossed, it must land as either **Heads** or **Tails**. That is a certainty.

*P(Heads) + P(Tails) = 1*