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

CHAPTER 2 • GRAPHS, CHARTS, AND TABLES—DESCRIBING YOUR DATA 77
three variables: number of U.S. employees; number of training hours per year per
employee; and total revenue in millions of dollars.
Company U.S. Employees Training Hr/Yr Revenues
Southwest Airlines 24,757 15 $3,400
Kingston Technology 552 100 $1,300
SAS Institute 3,154 32 $653
Fel-Pro 2,577 60 $450
TD Industries 976 40 $127
MBNA 18,050 48 $3,300
W.L. Gore 4,118 27 $1,200
Microsoft 14,936 8 $8,700
To better understand these companies, we might be interested in the relationship
between number of U.S. employees and revenue and between training hours and U.S.
employees. To construct these scatter diagrams, we can use the following steps:
Step 1 Identify the two variables of interest.
In the first case, one variable is U.S. employees and the second is revenue.
In the second case, one variable is training hours and the other is
U.S. employees.
Step 2 Identify the dependent and independent variables.
In each case, think of U.S. employees as the independent (x) variable. Thus,
Case 1: y revenue (vertical axis)
Case 2: y training hours
(vertical axis)
x U.S. employees
(horizontal axis)
x U.S. employees
(horizontal axis)
Step 3 Establish the scales for the vertical and horizontal axes.
The maximum value for each variable is
revenue $8,700 U.S. employees 24,757 training hours 100
Step 4 Plot the joint values for the two variables by placing a point in the
x, y space.
$10,000
$9,000
Scatter Diagram
Revenue (Millions)
$8,000
$7,000
$6,000
$5,000
$4,000
$3,000
$2,000
$1,000
General Positive Relationship
0
0
5,000
10,000
15,000
U.S. Employees
20,000
25,000
30,000