Explanation:
to calculate MAD you calculate the absolute distance between each data point and the mean. then take the average of those distances (sum them up and divide by the number of data points).
so, first we need the mean value of the data points :
(7 + 9 + 6 + 6) / 4 = 28/4 = 7.
the absolute distance of 7 to the mean value is 0.
the absolute distance of 9 to the mean value is 2.
the absolute distance of 6 to the mean value is 1.
the absolute distance of 6 to the mean value is 1.
the sum of these absolute distances is
0 + 2 + 1 + 1 = 4
MAD is then these 4 divided by 4 (the number of data points) :
4/4 = 1.