Key learning points

1. Summing the probabilities of all possible unique outcomes for a trial gives 1
2. Summing the probabilities of non-unique events gives a value not equal to 1
3. Knowing that the probabilities of all possible unique outcomes sum to 1 can be used to find unknown probabilities.
4. Knowing that probabilities can sum to 1 can be used to find unknown probabilities (different denominators).

Keywords

• Mutually exclusive - Two events are mutually exclusive if they share no common outcome.

Common misconception