Another useful measure of variation for a data set is the mean absolute deviation (MAD). It is calculated by the formula

MAD=|xx| /n. (I didn't know how to copy that put its divided by n or over n).

(a) Find the mean absolute deviation of the data set 18, 18, 19, 19, 20, 17, 19, 17, 21, 23, 21, 17, 17, 19, 19, 17, 20, 23, 18.

Compare the result with its sample standard deviation

s1.9.

I understand the first step is the sum of the numbers divided by the amount of numbers. so, 362/19=19.05 Then I get confused with the book.