Otherwise known as MAD
MAD—what is it?
 Mean Absolute Deviation is used to find
out how much data varies from the mean
of that data set.
 So its not just finding the mean once, its
kind of like finding the mean of the mean
(you’ll see what this means in a second).
 The answer will always be one number.
 Outliers do not have a big impact on the
MAD.
MAD-what does it mean?
 The higher the MAD, the greater
variability there is in the data
(variability is how spread out or how
clustered a group of data is).
 High variability means the data is
really spread out.
 Low variability means the data is
really close together.
MAD-how do you find it?
This calculation has 3 steps to it.
We will slowly walk you through
each step using this problem:
Sara took 6 tests last quarter. Her 6
test scores are 93, 84, 72, 65, 77,
and 89 percents.
Sara took 6 tests last quarter. Her 6 test scores
are 93, 84, 72, 65, 77, and 89 percents.
 Step 1.) Find the mean of the data.
 Add up 93 + 84 + 72 + 65 + 77 + 89
 You should get 480
 Divide 480 by 6 since there are 6 tests.
 You should get 80.
So the 1st mean is 8o. Don’t forget
this!
Sara took 6 tests last quarter. Her 6 test scores
are 93, 84, 72, 65, 77, and 89 percents.
 Step 2.) Find out how far away each piece of data is
from the 1st mean (which was 80, remember?)
Original Test Distance Away from 80
Score
93
13
84
4
72
8
65
15
77
3
89
9
Sara took 6 tests last quarter. Her 6 test scores
are 93, 84, 72, 65, 77, and 89 percents.
 Last step…finally! 
 Now you find the mean AGAIN, this time of the new
numbers from step 2.
Add up
13+4+8+15+3+9
Distance Away
from 80:
13
4
8
15
3
9
Find
Mean
This equals 52
Divide 52 by 6 since
there are 6 numbers
This equals 8.67
(rounded)
You are done!
 So the Mean Absolute Deviation of Sara’s
test scores is 8.67.
 This means (no pun intended) that the
average distance each of Sara’s test scores is
away from the original mean of 80 is 8.67
percentage points.
Your turn… 
Use the chart we provided to help
you organize your work when
finding the MAD of your Graph It
survey data.