now we find the absolute value of the difference between the data set and the mean | 21 - 15 | = 6 |10 - 15 | = 5 |15 - 15 | = 0 |19 - 15 | = 4 |8 - 15 | = 7 | 17 - 15 | = 2 | 15 - 15 | = 0
now we find the mean (average) of these numbers (6 + 5 + 0 + 4 + 7 + 2 + 0) / 7 = 24/7 = 3.43 <=== the MAD