Statistical Terms mean - the average of all data collected. Determining dispersion 1. Mean deviation is the average deviation from the mean. It is a weak indicator of dispersion and is seldom used in statistics. It can be used to compare dispersion in two or more experiments.
Variance is the average sum of the squares of the deviations from the mean.
It is designated by the lower case Greek letter sigma 2 and is used to calculate the more popular statistic called standard deviation. Standard Deviation, sigma, is a measure of dispersion about the mean that allows us to predict what percentage of data points should be expected at various deviations from the mean. Find the mean. Find the range. Find the median.