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

34 CHAPTER 2 • GRAPHS, CHARTS, AND TABLES—DESCRIBING YOUR DATA
TABLE 2.2 Atlanta Store Product
Categories Frequency
Distribution
Number of
Product
Catagories
Frequency
1 25
2 29
3 42
4 92
5 83
6 71
7 35
8 19
9 29
10 18
11 7
Total 450
TABLE 2.3 Frequency Distributions of Years of College Education
Dallas
Knoxville
Years of College Frequency Years of College Frequency
0 35 0 187
1 21 1 62
2 24 2 34
3 22 3 19
4 31 4 14
5 13 5 7
6 6 6 3
7 5 7 4
8 3 8 0
Total 160 Total 330
Relative Frequency
The proportion of total
observations that are in a given
category. Relative frequency
is computed by dividing the
frequency in a category by the
total number of observations.
The relative frequencies can be
converted to percentages by
multiplying by 100.
of years of college attended. The responses ranged from zero to eight years. Table 2.3
shows the frequency distributions for each city.
Suppose now we wished to compare the college years distribution for Dallas with
that for Knoxville. How do the two cities’ distributions compare? Do you see any difficulties
in making this comparison? Because the surveys contained different numbers of
people, it is difficult to compare the frequency distributions directly. When the number of
total observations differs, comparisons are aided if relative frequencies are computed.
Equation 2-1 is used to compute the relative frequencies.