Mean absolute deviation, standard deviation and variance are all measures of the variability of a data set. The absolute and mean absolute deviation display the quantity of deviation or variation that arises about the mean score. To discover the total variability in our group of data simply add up the deviation of each score from the mean. The average deviation of a score can then be considered by dividing the total by the number of scores. To calculate the deviation of a score from the mean rest on on choice of statistic whether by means of absolute deviation, variance or standard deviation.
