What you'll learn
Calculating the chance of events.
Key skills
- Probability from 0 to 1; the complement P(not A) = 1 − P(A).
- Mutually exclusive events: add probabilities.
- Independent events: multiply probabilities.
- Tree diagrams (with and without replacement) and expected frequency.
Exam tips
- Check whether events are with or without replacement.
- Multiply along tree branches; add outcomes for 'or'.
Common mistakes
- Adding when you should multiply.
- Forgetting probabilities change in 'without replacement' problems.