Question

how do i find the mean absolute deviation? my math textbook sucks

Answer 1

this explains how
http://www.mathsisfun.com/data/mean-deviation.html

step 1) find the mean (i.e. average) of your numbers
step 2) subtract the mean from each of your numbers. *Ignore the sign*
step 3) find the mean of the numbers you get from step 2

Example:
1 2 9
step 1: find the mean: (1+2+9)/3 = 12/3 = 4
step 2: make a new list by subtracting 4 from each of 1, 2, and 9.
(4-1), (4-2), (9-4) or 3,2,5
step 3: find the mean of the list from step 2: (3+2+5)/3 = 10/3 = 3.333

notice in step 2, it's easiest if you do "big number" minus "small number"