Topic explanation
Understand and use conditional probability, including the use of tree diagrams.
Key formulas & rules
- P(event) between 0 and 1; sample spaces and equally likely outcomes
- Addition for mutually exclusive events; multiplication for independent events
- Tree diagrams: multiply along branches; add end-to-end for OR across branches
Common mistakes
- Arithmetic and sign errors when simplifying expressions involving conditional probability.
- Not answering in the required form (fraction vs decimal, surd vs rounded).
- Missing a final sentence that interprets the result in context when the question is applied.
Exam tips
- Underline key words in the question: “exact”, “integer”, “give reasons”.
- Estimate or use inverse operations to sanity-check answers when a calculator is allowed.
- Use StudyVector practice filtered to “Conditional Probability” to drill exam-style questions on this skill.
Practice questions
Exam-style questions aligned to your board. Open full practice for worked feedback and your next best question.
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