Mean absolute deviation is the mean of the numbers and then the mean of that.
Example: The data set 1,2,3,4,5,6 has mean of 3.5 now you subtract the mean from all the numbers in the data set thus getting the following, 2.5,1.5,.5, .5 , 1.5, 2.5. Then you find the mean of those numbers thus getting the mean absolute deviation.
