The midrange of a data set consisting of a list of numbers is the average of the maximum and minimum.

If the data is grouped into classes the midrange may not be calculated exactly. Suppose we have the frequency distribution below.

The smallest tree could be as low as 60 feet tall and the tallest as low as 85.

The midrange could be as small as

The smallest tree could be as tall as 65 feet tall and the tallest as tall as 90.

The midrange could be as small as

The best estimate of the midrange is found by usung the midpoints of the shortest and tallest frequency classes – 62.5 and 87.5 respectively, giving