Higher

# Draw a tree diagram for dependent events

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## Lesson details

### Key learning points

- In this lesson, we will learn how to draw tree diagrams and complete missing probabilities in tree diagrams for dependent events.

### Licence

This content is made available by Oak National Academy Limited and its partners and licensed under Oak’s terms & conditions (Collection 1), except where otherwise stated.

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### 3 Questions

Q1.

For the probability tree shown, which calculation will find the probability of red followed by blue happening?

0.2 + 0.2

0.2 x 0.2

0.8 x 0.8

Q2.

The probability that Amy and Joe win a game of chess is shown in the tree diagram. Work out the probability that over 2 games Amy wins twice.

0.49

0.6

0.9

Q3.

James draws this probability tree diagram to help him calculate probabilities of taking sweets from a bag. What assumptions has James made when completing this probability tree?

All probabilities add to 1 on each branch.

It doesn’t matter if he eats the first sweet he takes.

### 3 Questions

Q1.

Probability of a dependent event is also called?

Biased probability.

Mutually exclusive.

Random probability.

Q2.

Simon has drawn this probability tree for a question on dependent probability. What mistake has he made?

The fractions on each branch do not sum to 1.

The probabilities should be decimals.

Q3.

This tree diagram shows Amir taking red and blue sweets from a bag. He does not replace the sweet after he has taken one.

A

B

D