Branching Out into Probability
Branching Out into Probability
Imagine you're planning a journey with multiple stops. At each junction, you have different routes to choose from. Tree diagrams work like roadmaps for probability - they show all possible paths through multi-stage events, making it easy to calculate the probability of any specific route.
From weather forecasting to sports tournaments, tree diagrams help us visualize complex probability scenarios step by step.
Mathematics glossary
- What is a tree diagram?
- A visual representation of all possible outcomes in multi-stage events
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Exam Tips
- Check probabilities add to 1 at each branching point
- Label all branches clearly with both outcome and probability
- Use fractions when possible - they're often easier to multiply than decimals
- Identify the type - with or without replacement affects subsequent probabilities
- Multiply along paths - for specific sequences
- Add across paths - for combined events
- Double-check final probabilities - all outcomes should sum to 1
Now try it yourself
Quiz · Question 1 of 15
A fair coin is flipped twice. In a tree diagram, what must the probabilities on the branches from the same point always add up to?
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This topic in real past papers
Every real exam question we've found on tree diagrams, with a full worked answer.
AQA Paper 1
Two of the four sittings we have full papers for build a tree diagram problem with two stages, both requiring the branches to be completed before any calculation.
Edexcel Paper 1
Two of the three sittings we have full papers for test combined probability of independent events, once forwards using a tree diagram and once backwards from a stated combined probability.
Edexcel Paper 2
Two of the three sittings we have full papers for combine the probability of the same event happening twice, once using a given probability with a tree diagram, and once using an estimated probability from a frequency table.