The population is then described in terms of this central point. Mean is the sum of all values divided by the total number of observations. Median is the middle value in a set of data which is sequentially ordered. Variation Variation is a measure of the dispersion or spread of the data in the population. Variance equals an average squared difference from the mean.
Standard deviation is the positive square root of variance.
Standard deviation is often more useful since it's a value in the same scale as the original data. Coefficient of variation is the ratio of standard deviation to the mean. This is a relative measure which facilitates comparison of dispersion between two populations whose values are in different scales. Shape is determined by comparison of mean and median.