In today's information rich community it is important to get ideas across in an engaging and efficient form. You have probably come across many infographics in advertisements, magazines and presentations. An infographic is a collection of imagery, charts, and minimal text that strives to give an appealing and easy-to-understand overview of a topic. Below is an infographic about travel to the moon containing information that is represented in many different ways.
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| Infographic on visiting the Moon |
To read infographics effectively you need skills in interpreting many different types of graphs. In this lesson we will look at interpreting a few familiar and unfamiliar charts that are often used.
Pie charts
A pie chart (pie graph or sector graph) is a special chart that uses a circle divided into slices(sectors) to show relative sizes of data. This chart is useful to display and compare parts of data that make up a whole, such as proportion of voters voting for particular political parties.
There are $360^\circ$360° in a circle. Using this fact we can:
- Find the angle, ($\theta$θ), for segments knowing fraction of the whole the segment represents:
$\theta=\text{Fraction of group in sector}\times360^\circ$θ=Fraction of group in sector×360°
- Find the number a segment represents:
$\text{Number in a sector}=\frac{\theta}{360}\times\text{Number in whole group}$Number in a sector=θ360×Number in whole group
Practice question
Question 1
The sector graph represents the number of people taking leave from work at a particular company.
If $5$5 people took leave in January, how many degrees represent $1$1 person?
How many people took leave in November?
How many people took leave between the beginning of November and the end of March?
What percentage of the people took leave in December?
Give your answer as a percentage, rounding to two decimal places.
Segmented bar charts
A segmented bar chart is a graph where the bar represents the whole data set and the bar is divided into several segments to represent the proportional size of each category. It is very similar to a pie chart but with a bar replacing the circle.
Practice question
Question 2
The divided bar graph below shows the popularity of certain types of restaurants in Valentina's home town.
Which restaurant is the most popular?
Mexican restaurant.
AItalian restaurant.
BThai restaurant.
CFrench restaurant.
DDo more people go to French restaurants or to Thai restaurants?
French restaurants
AThai restaurants
BWhich two restaurants are visited by the same number of people?
Mexican and Indian
AIndian and Thai
BThai and Italian
CIndian and French
DIf $24$24 people went to an Indian restaurant, approximately how many went to a Mexican restaurant?
$0$0
A$24$24
B$48$48
C$96$96
D
Bar graphs
A bar graph always presents a categorical data set. There is one column per category, and the height of each column is the size of that category. There is usually a small gap between each column.
Both axes should be labelled to provide additional information about the data and tell us what type of values we have.
Practice question
Question 3
Study the bar graph below, which shows the changes in tourism rates in different cities during 2011 and 2012 , then answer the following questions.
What is the difference between Shanghai's percentage of tourism over the 2 years?
$25%$25%
A$10%$10%
B$20%$20%
C$15%$15%
DWhich city had the greatest difference in percentages of tourism over 2011 and 2012?
London
ATokyo
BRome
CNew York
DWhich city had the smallest difference in minimum and maximum percentages of tourism over 2011 and 2012?
Singapore
AIstanbul
BDubai
CParis
DWhat is the difference between the minimum and maximum percentages of tourism of all the cities in the graph over the 2 years.
$55%$55%
A$65%$65%
B$40%$40%
C$60%$60%
D