Relative standard deviation is the percentage form of the coefficient of variation. Like variance, relative standard deviation is a measure of how densely packed a data set is. A small relative standard deviation points to a data set that does not deviate very much from the mean. A large relative standard deviation indicates a data set that is spread out, with many pieces of data far from the mean. Relative standard deviation is used to compare how spread out different data sets are from each other, providing a standardized way to easily compare the density of different data sets.