In this chapter, we will look at some charts
and graphs used to summarize categorical
data.
A table of the form:
Category
Frequency
Relative Frequency
= the count or number in the sample falling into the
category value
= the percentage of the sample that falls into
the category value
relative frequency =
frequency
n
Construct a frequency table for eye color using the
data from “ACSC”.
A graphical version of a frequency table:
• the horizontal axis has each category value (in any order) equally
spaced apart
• the vertical axis should be appropriately scaled, and it represents
either the frequencies or relative frequencies
• rectangles (of equal width) are then drawn above each category
with heights corresponding to each frequency or relative
frequency
Construct a bar chart for eye color using the data from
“ACSC”.
A circular version of a bar chart:
Each category value is graphed with its appropriate
“wedge size” in a circle rather than bars/rectangles
side by side.
wedge size = ( relative frequency) ´ 360
Construct a pie chart for eye color using the data from
“ACSC”.
A two-way table that gives the frequencies (or relative
frequencies) for 2 categorical variables simultaneously:
The table shows the frequencies of 120 movies
released in 2005 based on genre and rating.
G
PG
PG-13
R
Action
4
5
17
9
Comedy
2
12
20
4
Drama
0
3
8
17
Horror
0
0
11
8
The table shows the frequencies of 120 movies
released in 2005 based on genre and rating.
G
PG
PG-13
R
Action
4
5
17
9
35
Comedy
2
12
20
4
38
Drama
0
3
8
17
28
Horror
0
0
11
8
19
6
20
56
38
120
The first thing we should do with such a table is fill in the totals.
The table shows the frequencies of 120 movies
released in 2005 based on genre and rating.
G
PG
PG-13
R
Action
4
5
17
9
35
Comedy
2
12
20
4
38
Drama
0
3
8
17
28
Horror
0
0
11
8
19
6
20
56
38
120
(a) What percentage of the movies were comedies?
The table shows the frequencies of 120 movies
released in 2005 based on genre and rating.
G
PG
PG-13
R
Action
4
5
17
9
35
Comedy
2
12
20
4
38
Drama
0
3
8
17
28
Horror
0
0
11
8
19
6
20
56
38
120
(b) What percentage of the movies were rated PG?
The table shows the frequencies of 120 movies
released in 2005 based on genre and rating.
G
PG
PG-13
R
Action
4
5
17
9
35
Comedy
2
12
20
4
38
Drama
0
3
8
17
28
Horror
0
0
11
8
19
6
20
56
38
120
(c) What percentage of the dramas were rated R?
The table shows the frequencies of 120 movies
released in 2005 based on genre and rating.
G
PG
PG-13
R
Action
4
5
17
9
35
Comedy
2
12
20
4
38
Drama
0
3
8
17
28
Horror
0
0
11
8
19
6
20
56
38
120
(d) What percentage of PG-13 movies were Horror
films?