Chapter 2: Graphs, Charts, and Tables--Describing Your Data

36 CHAPTER 2 • GRAPHS, CHARTS, AND TABLES—DESCRIBING YOUR DATA
SUMMARY Developing Frequency and Relative Frequency Distributions for Discrete Data
To develop a discrete data frequency distribution, perform
the following steps:
1. List all possible values of the variable. If the variable is
ordinal level or higher, order the possible values from
low to high.
2. Count the number of occurrences at each value of
the variable and place this value in a column labeled
“frequency.”
To develop a relative frequency distribution, do the
following:
3. Use Equation 2.1 and divide each frequency count by the
total number of data values and place in a column headed
“relative frequency.”
EXAMPLE 2-1 Frequency and Relative Frequency Distributions
TRY PROBLEM 2.3
International Airline Travel Following the tragic events of September 11, 2001,
there was a sharp reduction in international travel by U.S. citizens. A travel magazine
recently surveyed 16 business executives to determine how many international trips they
made in 2006. The following data were observed:
3 0 0 1
1 2 2 0
0 2 1 0
2 1 4 2
The editors wish to construct a frequency distribution and a relative frequency distribution
for the number of international trips taken by these executives.
Step 1 List the possible values.
The possible values listed in order for the discrete variable are 0, 1, 2, 3,
4.
Step 2 Count the number of occurrences at each value.
The frequency distribution follows:
International Trips Frequency Relative Frequency
0 5 5/16 .3125
1 4 4/16 .2500
2 5 5/16 .3125
3 1 1/16 .0625
4 1 1/16 .0625
Total 16 1.0000
Step 3 Determine the relative frequencies.
The relative frequencies are determined by dividing each frequency by
16, as shown. Thus, just over 31% of those responding took no trips
during 2006.