The average
deviation is one of several indices of variability that statisticians use to characterize
the dispersion among the measures in a given population.
To calculate the average deviation of a set of scores it is first necessary
to compute their mean and then specify the distance between between each
score and that mean without regard to whether the score is above or below
the mean. The average deviation is defined as the mean of these absolute
values.
Algebriacally the average
deviation is specified as follows: