1. Unit 2 – Data Analysis & Interpretation
Consumer Mathematics 30S
Using Circle Graphs to Represent Data
2. Circle Graphs
Another way to display data is in the form of a circle
graph or pie chart. Circle graphs are useful in
displaying percentages, or parts of a whole.
Unit 2 – Data Analysis & Interpretation
Consumer Mathematics 30S
3. Circle Graphs
Unit 2 – Data Analysis & Interpretation
Consumer Mathematics 30S
Properties of Circle Graphs:
• They are circular shaped graphs with the entire circle
representing the whole.
• The circle is then split into parts, or sectors.
• Each sector represents a part of the whole.
• Each sector is proportional in size to the amount each
sector represents, therefore it is easy to make
generalizations and comparisons.
4. Constructing Circle Graphs
Unit 2 – Data Analysis & Interpretation
Consumer Mathematics 30S
When constructing a circle graph, follow the steps below
1. Is the Data Suitable--Determine if there is a "whole" for the data. Then
determine what the different parts, or data groups, of the whole are.
2. Calculate Percentages--For data that is not already given as a percentage,
convert the amounts for each part, or data group size, into a percentage of the whole.
3. Draw the Graph--Draw a circle and draw in a sector for each data group.
4. Title and Label the Graph--Label the sectors with the data group name
and percentage. Then add a title to the graph. This is the same as the title of the table.
5. Example
Unit 2 – Data Analysis & Interpretation
Consumer Mathematics 30S
Construct a circle graph for the following data.
6. Constructing a Circle Graph
Unit 2 – Data Analysis & Interpretation
Consumer Mathematics 30S
Step 1 – Is the Data Suitable?
• There are five parts to the whole. Each data group is a
category of sneaker brands (1) Adidas, (2) Nike, (3)
Reebok, (4) Asics, (5) Other.
Step 2 – Calculate Percentages
• Calculate the whole: 150 + 192 + 60 + 108 + 90 = 600
• Calculate the percentage for each part
ex. Adidas: 150/600 = .25 or 25%
7. Constructing a Circle Graph
Unit 2 – Data Analysis & Interpretation
Consumer Mathematics 30S
Step 3 – Draw the Graph
• First, draw a circle. Then, draw in the sectors of the
circle using a protractor to calculate the size of the
sector.
• The percentage has to be converted to a degrees.
ex. 25% or .25 x 360o
= 90o
Step 4 – Title and Label the Graph
8. Can circle graphs be misleading?
Unit 2 – Data Analysis & Interpretation
Consumer Mathematics 30S
Classroom Activity: Page 118 - 119
