Higher

Higher

# Draw a tree diagram for dependent events

## Lesson details

### Key learning points

1. 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.

## Video

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## Worksheet

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## Starter quiz

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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.
Correct answer: He replaces the first sweet he takes.
It doesn’t matter if he eats the first sweet he takes.

## Exit quiz

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### 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.
Correct answer: The second part of the probability tree has incorrect probabilities.
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