In statistics, class size refers to the difference between the upper and lower boundaries of a class in a frequency distribution.

The following examples shows how to find the class size for various frequency distributions.

Example 1: Finding Class Size for Basketball Data

Suppose we have the following frequency distribution that describes the number of points scored by various basketball players in a league:

The first class has a lower limit of 1 and an upper limit of 5. Thus, the class size would be calculated as:

• Class size: 5 – 1 = 4

The second class has a lower limit of 6 and an upper limit of 10. Thus, the class size would be calculated as:

• Class size: 10 – 6 = 4

No matter which class we analyze in the frequency distribution, we’ll find that the class size is 4. 

Example 2: Finding Class Size for Sales Data

Suppose we have the following frequency distribution that describes the number of widgets sold by a certain company on different days:

The first class has a lower limit of 1 and an upper limit of 10. Thus, the class size would be calculated as:

• Class size: 10 – 1 = 9

The second class has a lower limit of 11 and an upper limit of 20. Thus, the class size would be calculated as:

• Class size: 20 – 11 = 9

No matter which class we analyze in the frequency distribution, we’ll find that the class size is 9. 

Additional Resources

How to Find Class Boundaries (With Examples)
How to Find Class Intervals (With Examples)
How to Find Class Limits (With Examples)