13B.3 - Tree Diagrams

Tree diagrams

Tree diagrams can be used to show the outcomes in a sample space containing two or more events. If you only need to represent two event you may also consider a table or grid. Each stage in the multi-stage experiment is represented by another set of forks in the tree.

Mathematical operations with tree diagrams

When using a tree diagram remember:

• Multiply probabilities along the branches.
• Add probabilities down the tree.

Helpful hints:

• Keep probabilities as unsimplified fractions so that you can check they all add up to 1. When you answer the question you should then simplify your answer!
• If the probabilities of the branches in the same "stage" are identical up and down the tree then you are dealing with independent events. If the the probabilities are different within the same stage the events are dependent.

13B.3 - Exercises:

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