How is the class midpoint calculated?

The class midpoint, or class mark, is calculated by adding the lower and upper limits of the class and dividing by two. The class midpoint is sometimes used as a representation of the entire class.

A class midpoint is halfway across the interval of a class, hence it is calculated by averaging the lower and upper limits. One Kobo provides an example of calculating the class midpoint; in a distribution where class intervals range in values: {1 to under 3, 3 to under 5, 5 to under 7, 7 to under 9, 9 to under 11, 11 to under 13} the class midpoints would be {2, 4, 6, 8, 10, 12} respectively. Each of these values are the average of the low and high extremes of each respective class.