Free IB Maths AI SL lesson: Combined events & sample-space diagrams
A ready-to-teach IB Maths AI SL lesson on Combined events & sample-space diagrams (Unit 4 · Statistics & Probability): editable slides and teacher notes, free; a printable worksheet in 3 levels with answers for school plans. About 55 minutes.
Free with a teacher account. Sign in with Google, Microsoft or email and download the slides and teacher notes.
What's inside
- Slides (PowerPoint, editable) · freeabout 12 slides: do now, objectives, key ideas, a worked example step by step, “your turn”, practice QR code, exit ticket
- Teacher notes (PDF) · freelesson plan with timings, common mistakes, homework links
- Worksheet (PDF) · school plans6 questions, 28 marks: Fluency, Reasoning, Exam-style. Included with school plans and the teacher trial.
- Answers (PDF) · school plansthe answer to every worksheet question, from its mark scheme. Included with school plans and the teacher trial.
Learning objectives
- Basic Probability, Venn Diagrams & Sample Spaces
- Tree Diagrams & Combined Events
- Sample Spaces & Expected Numbers of Outcomes
- Probability in Context: Harder Venn Diagram & Conditional Problems
- Expected Value in Games & Decisions
Key vocabulary
- sample space: The set of all possible outcomes.
- event: A set of outcomes.
- complement: A′, the event that A does not happen.
- mutually exclusive: Events that cannot both happen.
- population: The whole group being studied.
Common mistakes this lesson tackles
- Probability: adding instead of multiplying, conditional sample spaces, without replacement. Draw the tree or table. Along a branch multiply; between outcomes add. For "given that", the denominator is the size of the given group. Without replacement, the second probability changes.
- Basic statistics: range as an interval, frequency tables, outlier fences, Spearman's ranks. Range = largest − smallest (one number). Enter values and frequencies as two lists on the GDC. An outlier is beyond Q₁ − 1.5 × IQR or Q₃ + 1.5 × IQR; compare the actual data with the fence. Spearman's is between the ranks of the two variables.
- Adding P(A) + P(B) without subtracting the overlap.
Lesson plan
| 0–5 min | Do now: students write down what they remember about Chi-squared goodness-of-fit test and Chi-squared test for independence |
| 5–8 min | Share the learning objective and success criteria |
| 8–20 min | Teach: the worked example, step by step; students copy the method |
| 20–25 min | Your turn: 1 mini-whiteboard question; check every board before moving on |
| 25–42 min | Practise: the worksheet (6 questions in 3 levels, with school plans and the teacher trial) or the topic's practice questions online; move up a level after two right in a row |
| 42–47 min | Plenary: 1-question exit ticket; collect it to plan the next lesson |
For students: practise this topic
The worksheet's QR code opens the IB Maths AI SL Unit 4: Probability practice questions.
What schools get
- Set this lesson as homework, marked by AI against the mark scheme, with every result in your markbook (school Pro plan).
- This lesson's worksheet in three levels, with its answers, ready to print.
- Support, Core and Stretch versions and A/B copies of the worksheet from the full question bank, in the worksheet builder.
- Create lesson: this lesson rebuilt for your class's next scheme-of-work lesson, from the full bank.
School licences from €490 a year. Try everything free for 30 days as a teacher: no card.
Questions teachers ask
Is this lesson free?
The slides and the teacher notes are free to download with a free IB Math Revision teacher account (sign in with Google, Microsoft or email); no card. The printable worksheet in three levels and its answers are included with school plans and the free 30-day teacher trial.
Can I edit the slides?
Yes. The slides are an ordinary PowerPoint file: change, add or delete anything. They also open in Google Slides and Keynote. The logo and web address sit on the slide master, so your edits do not move them.
What do students use for homework?
The practice slide's QR code and web address take students to the IB Maths AI SL Unit 4: Probability practice questions on ibmathrevision.com, where the free questions are open and the full bank comes with a plan.