Question

Consider the following frequency table representing the scores on a test.

Scores on a Test
Class Frequency
40–47
13
48–55
11
56–63
10
64–71
4
72–79
6

Determine the class width of each class.

Answer 1

8

Explanation:

You want to know the class width associated with a frequency table that has classes defined by 40–47, 48–55, ....

Class width

The class width can be found by subtracting the lowest value in a class from the lowest value in the adjacent class:

48 -40 = 8

The class width is 8.

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Additional comment

The class width is usually defined in such a way that values can be unambiguously assigned to a class. Here, the 8 integer values {40, 41, 42, 43, 44, 45, 46, 47} are assigned to the class 40–47. The next higher integer value, 48, is assigned to the next class.

Sometimes, the class boundaries are defined as values that the data cannot have: 39.5–47.5, and 47.5–55.5, for example. In those cases, the class width is the difference between boundary values.

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