Probability of a single event
, when all outcomes are equally likely.
Definition. When all outcomes are equally likely:
Range. . means impossible; means certain.
Forms. Cambridge accepts fractions, decimals, or percentages. Don't mix notations within one answer.
Worked. Bag with red, blue, green balls. One drawn at random.
- .
- .
- (impossible).
- (certain).
Worked. Two fair dice rolled. Probability of total being .
- Sample space: ordered pairs.
- Favourable: β outcomes.
- .
- Probability = favourable / total (equally likely).
- Range .
- Use fractions, decimals, or %, not mixed.
- List the sample space if it's small.