This document discusses different measures of dispersion used to quantify the spread or variability in a data set. It defines dispersion and explains that measures of dispersion are used to measure how spread out values are, determine the reliability of averages, and compare the variability between data sets. The document outlines different types of measures, including absolute measures like range and mean deviation, and relative measures like coefficient of variation. It provides examples of calculating range, mean deviation, population variance, and standard deviation, and discusses their purposes and limitations.