Statistics for the Behavioral Sciences by Frederick J. Gravetter, Larry B. Wallnau ISBN 10: 1305504917 ISBN 13: 9781305504912

SECTION 2.3 | Frequency Distribution Graphs 43
FIGURE 2.2
An example of a frequency distribution
histogram. The same set of quiz
scores is presented in a frequency
distribution table and in a histogram.
Frequency
4
3
2
1
21
3 4 5
Quiz scores (number correct)
X
5
4
3
2
1
f
2
3
4
2
1
FIGURE 2.3
An example of a frequency
distribution histogram for
grouped data. The same
set of children’s heights is
presented in a frequency
distribution table and in a
histogram.
Frequency
6
5
4
3
2
1
30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45
Children’s heights (in inches)
X
44–45
42–43
40–41
38–39
36–37
34–35
32–33
30–31
f
1
2
4
6
2
3
4
2
A Modified Histogram A slight modification to the traditional histogram produces a
very easy to draw and simple to understand sketch of a frequency distribution. Instead of
drawing a bar above each score, the modification consists of drawing a stack of blocks.
Each block represents one individual, so the number of blocks above each score corresponds
to the frequency for that score. An example is shown in Figure 2.4.
Note that the number of blocks in each stack makes it very easy to see the absolute
frequency for each category. In addition, it is easy to see the exact difference in frequency
from one category to another. In Figure 2.4, for example, there are exactly two more people
with scores of X = 2 than with scores of X = 1. Because the frequencies are clearly displayed
by the number of blocks, this type of display eliminates the need for a vertical line
(the Y-axis) showing frequencies. In general, this kind of graph provides a simple and
concrete picture of the distribution for a sample of scores. Note that we often will use this
FIGURE 2.4
A frequency distribution
graph in which each individual
is represented by a
block placed directly above
the individual’s score. For
example, three people had
scores of X = 2. 1 2 3 4 5 6 7
x