Year 9 - Maths
Calculating theoretical probabilities from probability tree diagrams (one event)
Probability: theoretical probabilities
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This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
Unit Summary
In this unit we build upon the concept of likelihood to work more mathematically with more measurable probability using fraction and decimal representations to both interpret and calculate. We revisit and develop ways to represent and compare probabilities.
Lesson Summary
You will learn to find theoretical probabilities from a probability tree diagram showing the possible outcomes for one event.
Key Notes
- The probability of an outcome can be found by considering a probability tree diagram showing all possible outcomes.
- The probability of a set of outcomes can be found by considering a probability tree showing all possible outcomes.
- A probability tree can help us find a probability, even when the outcomes are not equally likely.
Vocabulary To Learn
- Probability tree: Each branch of a probability tree shows a possible outcome from an event or from a stage of a trial, along with the probability of that outcome happening.
Common Mistakes To Avoid
- A probability tree can only have two branches.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
The probability of an outcome can be found by considering a probability tree diagram showing all possible outcomes. The probability of a set of outcomes can be found by considering a probability tree showing all possible outcomes.
2. Use this key word in a maths sentence and explain it clearly. 'Probability tree'
Each branch of a probability tree shows a possible outcome from an event or from a stage of a trial, along with the probability of that outcome happening. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: A probability tree can only have two branches. Correction: A probability tree can have any number of branches on a layer, but the more branches you want to include, the trickier and less practical the probability tree is to draw and use.
More Lessons In This Unit
- Calculating theoretical probabilities from a table (one event) Study Guide
- Calculating theoretical probabilities from lists (one event) Study Guide
- Calculating theoretical probabilities from probability trees (two events) Study Guide
- Calculating theoretical probabilities from two-way tables (two events) Study Guide
- Calculating theoretical probabilities from Venn diagrams (one event) Study Guide
- Calculating theoretical probabilities from Venn diagrams (two events) Study Guide
- Checking listing possible outcomes Study Guide
- Comparing multiple representations to calculate theoretical probabilities Study Guide
- Comparing multiple representations to calculate theoretical probabilities for combined events Study Guide
- Problem solving with theoretical probability Study Guide
- Summing probabilities Study Guide
- The probability scale Study Guide
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