Another very popular question regarding univariate data is, How variable are the data points? or How spread out or dispersed are the observations? To answer these questions, we have to measure the spread, or dispersion, of a data sample.
The simplest way to answer that question is to take the smallest value in the dataset and subtract it by the largest value. This will give you the range. However, this suffers from a problem similar to the issue of the mean. The range in salaries at the law firm will vary widely depending on whether the CEO is included in the set. Further, the range is just dependent on two values, the highest and lowest, and therefore, can't speak of the dispersion of the bulk of the dataset.
One tactic that solves the first of these problems is to use the interquartile range.