4.75 is your answer because you add 2,8,10,12 and then divide it by 4 equals 8 . Then divide 2,8,10,12 by 8 gives you the total of 6,0,9,4 add all that gives you a total of 19/4 equals your answer of 4.75
The mean of the data is 2+8+10+12 / 4, or 8. The absolute deviations of 2, 8, 10, and 12 from the mean are 6, 0, 2, and 4, respectively. The mean absolute deviation is 6+0+2+4 / 4, which is 3.
