The word "class" has many specialized meanings in mathematics in which it refers to a group of objects with some common property (e.g., characteristic class or conjugacy class.)

In statistics, a class is a grouping of values by which data is binned for computation of a frequency distribution (Kenney and Keeping 1962, p. 14). The range of values of a given class is called a class interval, the boundaries of an interval are called class limits, and the middle of a class interval is called the class mark.

The following table summarizes the classes illustrated in the histogram above for an example data set.

REFERENCES:

Kenney, J. F. and Keeping, E. S. Mathematics of Statistics, Pt. 1, 3rd ed. Princeton, NJ: Van Nostrand, 1962.