A Level Maths: Probability Topic Summary and Resources
Video Lessons
Watch alongside the worksheet for the full lesson experience, then test your understanding with the lesson questions.
Revision Notes
Handwritten notes summarising the key ideas for each lesson. Ideal for quick review before a test.
Exam Questions
Past-paper-style questions organised by topic, with full mark schemes.
- Intro to Probability (OCR)
- Conditional Probability and Venn Diagrams (OCR)
- Conditional Probability and Venn Diagrams (Edexcel)
- Conditional Probability with Tree Diagrams and Two-Way Tables (OCR)
Drawn from OCR and Edexcel past papers but designed to be useful for students of all UK exam boards — including AQA and OCR MEI — unless a sheet is explicitly board-specific.
Before You Start This Topic
It will help if you are confident with the following:
- GCSE Maths Probability — tree diagrams, basic addition and multiplication rules from GCSE are assumed
- Statistical Sampling — helps connect probability to populations and samples
A Level Maths probability covers the foundations needed for the statistical distributions and hypothesis testing topics later in the Statistics strand. You work with events, calculate probabilities using the addition and multiplication rules, and use Venn diagrams and tree diagrams to organise complex situations. Year 2 extends this with Conditional Probability.
You understand and use the concepts of mutually exclusive events (cannot both happen, so $P(A \cap B) = 0$) and independent events (one does not affect the probability of the other, so $P(A \cap B) = P(A) \times P(B)$). You apply the addition rule $P(A \cup B) = P(A) + P(B) – P(A \cap B)$, and use Venn diagrams to visualise unions, intersections, and complements. You learn set notation — $A'$, $A \cup B$, $A \cap B$ — for describing events. Tree diagrams handle probability questions involving multiple stages, including problems where outcomes affect future probabilities (drawing without replacement, conditional events). You also critique probability models, recognising assumptions like 'the coin is fair' and considering the impact of relaxing them.
Probability is part of the Statistics strand of A Level Maths for AQA, Edexcel, OCR, and OCR MEI students.
Watch out for…
A few things to be careful with: $P(A \cap B) = P(A) \times P(B)$ only when $A$ and $B$ are INDEPENDENT — for general events use $P(A \cap B) = P(A) \times P(B|A)$; the addition rule $P(A \cup B) = P(A) + P(B) – P(A \cap B)$ needs the intersection subtracted to avoid double-counting; mutually exclusive and independent are NOT the same — they are usually mutually exclusive OR independent, but rarely both (only when one event has probability zero); and probabilities must be in $[0, 1]$ — if you compute something outside this range you have made an error.