The span (English range) is the simplest measure of dispersion in statistics and is calculated as the distance between the largest and the smallest measured value:
The span is not robust against outliers, it depends only on the extreme values and loses with increasing sample size information content. It is therefore mainly used for small sample sizes. It has the same units as the measurement values themselves Thus, the difference is meaningful, must have this metric scale level.
The range can be used in various ways to estimate standard deviations and specify upper limits for standard deviations.