To find the absolute deviation we first need to know the mean or average of data values in a dataset.
Then, taking each data element in turn, we work out its absolute deviation by measuring the “distance” between the data element and the mean. This distance is expressed as a positive number—how far away the data element is from the mean. So each data element will have its own absolute deviation from the mean (a sort of central value for the dataset). The mean absolute deviation is simply the mean or average of all the absolute deviations in the dataset. Do not confuse the mean absolute deviation with the standard deviation which is calculated differently, but could be the same.