You polled your friends to find out how many video
games they have at home. The numbers you found
are listed below. Find the interquartile range of
the data, and draw a box and whisker plot.
12, 16, 22, 31, 32, 35, 41, 47, 49
IQR = 25
Math I
UNIT QUESTION: How do you use
probability to make plans and predict
for the future?
Standard: MM1D1-3
Today’s Question:
How do you find the mean absolute
deviation (MAD) of a data set?
Standard: MM1D3.a.
SAD to MAD
 SAD stands for the Sum of the Absolute
values of the Deviation
 MAD stands for the Mean of the Absolute
values of the Deviation
Did the SAD to MAD task. NOTE:
•Both are a measure of spread from the mean.
•Both are used to compare sets of data.
•SAD is OK if the sets of data have the same
number of data points.
•SAD will make the data set with the larger
number of points appear to have more spread.
•MAD is SAD ÷ N, where N is the number of data
points – that is why MAD is also called the
Mean (think average) Deviation
•MAD normalizes the data to eliminate the bias
of one data set having more points than another
Both are a measure of spread from the mean.
Notes on calculating SAD:
1. Find the mean of the data
2. Subtract the mean from each data point
3. Take absolute value of the differences
4. Add all the absolute values together
MAD = SAD / N
The mean absolute deviation of a numerical data set is
the average deviation of the data from the mean.
Mean Absolute Deviation 
x1  x  x2  x  ...  xn  x
n
The numbers below are the golf scores for the UGA golf
team. Find the mean absolute deviation of the data.
68, 70 , 72, 73, 74, 75
Mean = 72
68  72  70  72  72  72  73  72  74  72  75  72
2
6
Do the same for Georgia Tech: 66, 69, 70, 71, 74, 76
The numbers below are the total points for the Woodland
basketball team in its last 10 games. Find the Mean
Absolute Deviation.
72, 75, 73, 99, 68, 79, 48, 60, 52, 59
11.1
Homework
Pg 365, # 9 – 12 all, 15 and 16