Page 26 - 2024-bfw-starnes-TPS7e-SE proofs.indd

SecTIoN 1B Displaying and Describing Categorical Data 13

Use a pie chart when you want to emphasize each category’s relation to the
whole. Each slice of the pie shows the count or percentage of individuals in that
category. Pie charts are challenging to make by hand, but technology will do the
job for you.
A bar graph or pie chart that displays a distribution of categorical data must
caution
include all individuals in the data set. This might require including an “Other”
© 2024 BFW Publishers PAGES NOT FINAL - For Review Purposes Only - Do Not Copy

category, as in the radio station example. Bar graphs are more flexible than pie
charts. Both types of graphs can display the distribution of a categorical variable,
but a bar graph can also compare any set of quantities that are measured in the
same units.

comparing Distributions of categorical Data

You can use a bar graph to display the distribution of a categorical variable. A
side-by-side bar graph can be used to compare the distribution of a categorical
variable in two or more groups.

DEFINITION Side-by-side bar graph
A side-by-side bar graph displays the distribution of one categorical variable in
each of two or more groups.

It’s a good idea to use relative frequencies when comparing data for multiple
groups, especially if the groups have different sizes.

Screen time for teens and tweens Skill 2.D
EXAMPLE comparing distributions of

categorical data

PROBLEM: How much time do tweens (ages 8–12) and teens (ages
13–18) spend using digital devices each day? Researchers surveyed a
random sample of more than 1300 U.S. 8- to 18-year-olds to find out.
The side-by-side bar graph summarizes the data on daily screen time
reported by the 560 tweens and 746 teens in the sample. 11
45
40
35 Daily screen Melanie Acevedo/DigitalVision/Getty Images
time (h)
30
Percent 25 None
<2
20
2 to <4
15
4 to <8
10 8+
5
0
Teens Tweens
Age group

Compare the distributions of daily screen time for teens and tweens.

© 2024 BFW Publishers PAGES NOT FINAL - For Review Purposes Only, all other uses prohibited - Do Not Copy or Post in Any Form.

02_StarnesTPS7e_40934_un01_p1_001_086_6pp.indd 13 13/09/23 5:36 PM