Mutually Exclusive Events
(KS3, Year 7)
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
A Note on Notation
The probability of an event can be written as:
P(Event)
A letter or symbol can be used to represent an event.
For example, let H be the event that a coin lands on Heads when it has been tossed.
We can denote the probability of getting heads as:
P(H)
Many Events Are Not Mutually Exclusive
Many events are not mutually exclusive. It is possible to be male and have brown hair. It is possible for it to be a Monday and for it to be raining outside.Worksheet
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