1. Mean Absolute Deviation
MAD
a measure of data dispersion
Tells us how far away the numbers in a data set are from the mean
Works well for data that has outliers

2. Mean Absolute Deviation

3. Outlier
A data point which is far removed in value from the others in the data set
It is an unusually large or an unusually small value compared to the others.

4. The score of 20 would be an outlier.
Outlier Example
Test scores for 6 students were :
84, 92, 88, 79, 91 and 20.
The score of 20 would be an outlier.

5. Mean Absolute Deviation
1. Find the mean of the data.
Subtract the mean from each value –
the result is called the deviation from
the mean.
Take the absolute value of each
deviation from the mean.
4. Find the sum of the absolute values.
5. Divide the total by the number of items.

6. Find the mean absolute deviation
Test scores for 6 students were : 85, 92, 88, 80, 91 and 20.
Find the mean:
( )/6=76
2. Find the deviation from the mean:
85-76= = =12
80-76= = =-56

7. Find the mean absolute deviation
Test scores for 6 students were :
85, 92, 88, 80, 91 and 20.
3. Find the absolute value of each deviation from the mean:

8. Find the mean absolute deviation
Test scores for 6 students were :
85, 92, 88, 80, 91 and 20.
4. Find the sum of the absolute values:
= 112
5. Divide the sum by the number of
data items:
112/6 = 18.7
The mean absolute deviation is 18.7.

9. Find the mean absolute deviation
Test scores for 6 students were : 85, 92, 88, 80, 91 and 74.
Find the mean:
( )/6=85
2. Find the deviation from the mean:
85-85= = =3
80-85= = =-11

10. Find the mean absolute deviation
Test scores for 6 students were :
85, 92, 88, 80, 91 and 74.
3. Find the absolute value of each deviation from the mean:

11. Find the mean absolute deviation
Test scores for 6 students were :
85, 92, 88, 80, 91 and 74.
4. Find the sum of the absolute values:
= 32
5. Divide the sum by the number of
data items:
32/6 = 5.3
The mean absolute deviation is 5.3.

12. Which girl had the greater mean deviation for her scores?
Emma and Sara play 5 games on a handheld video game and record their scores in this table.
Game
Emma
Sara 1 30 15 2 20 25 3 10 4 5
Which girl had the greater mean deviation for her scores?

13. First, let’s look at Emma’s scores
Game
Emma 1 30 2 20 3 10 4 5
Find the mean
Find the deviation form the mean
Take the absolute value of each deviation
Find the sum of the absolute values
Divide the sum but the number or items

14. Now, Let’s look at Sara’s Scores
Find the mean
Find the deviation form the mean
Take the absolute value of each deviation
Find the sum of the absolute values
Divide the sum but the number or items
Game
Sara 1 15 2 25 3 20 4 5

15. Now let’s compare the deviations
What was the MAD of Emma’s scores?

16. What is Greg’s mean tip money?
Hourly Tips
What is Greg’s mean tip money?
What is Trent’s mean tip money?
What is the mean of the combined tip money?
Greg
Trent
$15
$20
$24
$22
$26
$18
$17

17. What is MAD of the combined tip money?
Hourly Tips
What is MAD of the combined tip money?
What is Trent’s MAD?
What is Greg’s MAD?
Greg
Trent
$15
$20
$24
$22
$26
$18
$17

18. Whose MAD is closer to the MAD of the combined tip money?
Hourly Tips
Greg
Trent
$15
$20
$24
$22
$26
$18
$17
Whose MAD is closer to the MAD of the combined tip money?