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

40 CHAPTER 2 • GRAPHS, CHARTS, AND TABLES—DESCRIBING YOUR DATA
TABLE 2.7 Frequency Distribution of DVD Movies Owned
DVD Movies Owned
Frequency
0 8
1 8
2 22
3 22
4 11
5 13
6 12
7 14
8 5
9 19
10 14
11 9
12 8
13 12
14 8
15 12
16 6
17 7
18 2
19 3
20 2
21 4
22 1
23 1
24 3
25 3
26 0
27 0
28 0
29 0
30 1
Total 230
Class Width
The distance between the lowest
possible value and the highest
possible value for a frequency
class.
Remember, these are only guidelines for the number of classes. There
is no specific right or wrong number. In general, use fewer classes for
smaller data sets; more classes for larger data sets. However, using too few
classes tends to condense data too much, and information is lost. Using too
many classes spreads out the data so much that little advantage is gained
over the original raw data.
Step 2 Establish the class width.
The minimum class width is determined by Equation 2.2
Class Width
Largest ValueSmallest Value
W
Number of Classes
(2.2)