Topics
14. Data
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AustraliaNSW
Stage 3

14.05 Dot plots

Lesson
Practice
Lesson

Are you ready?

Can you read information from a  picture graphs  ?

Examples

Example 1

A poll was taken to find people's favorite cupcake flavors. The votes are shown in the picture graph.

This image shows a picture graph. Ask your teacher for more information.
a

How many people voted for Strawberry?

Worked Solution
Create a strategy

Use the pictures in the table to find the number of votes.

The image says Remember that a cupcake represents 3 votes.
Apply the idea

There are 3 cupcakes next to strawberry. Since each cupcake represents 3 votes, we need to find 3 lots of 3.

\displaystyle \text{Votes}\displaystyle =\displaystyle 3\times 3Multiply 3 by 3
\displaystyle =\displaystyle 9

9 people voted for Strawberry.

b

What was the most popular cupcake flavor?

Worked Solution
Create a strategy

Choose the flavor that has the most cupcakes next to it.

Apply the idea

Chocolate Chip has the most cupcakes.

Chocolate Chip is the most popular cupcake flavor.

Idea summary

Look for the key to know the value of each picture in a picture graph.

Create and interpret a dot plot

This video looks at how to make a dot plot from information provided in a table.

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This video shows us how we can use a dot plot to interpret the results or answer specific questions about the data.

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Examples

Example 2

A group of adults is asked: "How old were you when you passed your driving test?".

The responses were:

17,\,17,\,20,\,17,\,22,\,18,\,22,\,18,\,22,\,18,\,22,\,17,\,19,\,18,\,18

a

Create a dot plot to find the most common age for someone in the group to have passed their driving test.

Worked Solution
Create a strategy

Draw a dot above the value of each age.

Apply the idea

The ages range from 17 to 22, so the numbers 17,\, 18,\, 19,\, 20,\, 21,\, 22 should be written on the axes of the dot plot.

A dot plot with 4 dots on 17, 5 dots on 18, 1 dot on 19 and 1 on 20, and 4 dots on 22.

The age 17 appears 4 times we draw 4 dots above 17.

The age 18 appears 5 times we draw 5 dots above 18.

Continuing this way gives us the dot plot shown.

Since 18 has the most dots above it, the most common age for someone in the group to have passed their driving test was 18.

b

How many people passed their driving test on or after their 19th birthday?

Worked Solution
Create a strategy

Count the number of dots above 19, \, 20, \, 21, and 22.

Apply the idea
\displaystyle \text{People}\displaystyle =\displaystyle 1+1+0+4Add the number of dots
\displaystyle =\displaystyle 6

6 people passed their driving test on or after their 19th birthday.

Idea summary

Dot plots show us how many of something, using dots. The key is really important, because it tells us if each dot is worth 1, or more than 1.

Outcomes

MA3-18SP

uses appropriate methods to collect data and constructs, interprets and evaluates data displays, including dot plots, line graphs and two-way tables

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