Range

The range is the simplest measure of spread: the largest value minus the smallest value. If test scores run from 41 to 98, the range is 57 points.

Its appeal is how easy it is to compute and explain, but it is fragile because it depends only on the two most extreme points — a single typo or outlier can blow it up. For that reason the range is best used as a quick sanity check (does the data even fall in a plausible band?) rather than as a serious description of how spread out the bulk of the data is.