Lauretta J. Fox
Many people find it easier to obtain information from pictures than from written material. Statisticians display mathematical relationships with diagrams and graphs. From these pictures numerical data can be summarized clearly and easily.
When the data of a frequency distribution have not been grouped in intervals, they can be represented on a dot
diagram
. A dot diagram illustrates the pattern of a distribution. It clearly shows whether the data are spread out evenly or if they tend to cluster about any point.
To construct a dot diagram list the measurements, from lowest to highest, horizontally across the bottom of the graph. On the left side vertically list the frequencies or number of times that the measurements occur. For each time a measurement occurs place a dot in the column above the measurement.
Example
:
Construct a dot diagram to represent the following distribution of daily temperature highs in twentyfour cities of the United States.
67

68

69

70

70

71

71

71

72

72

72

74

74

74

74

76

76

76

76

80

80

80

84

85

Solution
:
(figure available in print form)
Exercises
:

1.) Twenty workers were rated on a scale of 1 to 10 for efficiency. Construct a dot diagram to represent the following ratings: 7, 8, 9, 4, 5, 5, 7, 10, 6, 8, 7, 7. 5, 6, 9, 6.

2.) Draw a dot diagram to represent the following scores received on a spelling test: 98, 100, 78, 75, 68, 62, 75, 80, 82, 94, 80, 72, 75, 85, 85, 80, 70, 82, 78, 78, 72, 70, 90, 65.

3.) The distribution of heights of fifteen children is given below. Show the distribution on a dot diagram.
Height
in
Inches

Frequency

56

2

58

3

60

7

62

2

64

1
