Post on 13-Dec-2015
MEAN ABSOLU
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DEVIATI
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FIND MEAN ABSOLUTE DEVIATION
You have used range and the interquartile range to describe the spread of a set of data. You can also use the mean absolute deviation. The mean absolute deviation of a set of data is the average distance between each data value and the mean.
EXAMPLE
The Table shows the maximum speeds of eight roller coasters. Find the mean absolute deviation of the set of data. Describe what the mean absolute deviation represents.
Maximum speeds of roller coaster (MPH)
58 88 40 60
72 66 80 48
STEP 1
Find the mean = = 64
STEP 2
Find the absolute value of the difference between each value in the data set and the mean. (How far each number or piece of data is from the mean.)
This gives us the absolute value (how far each number is from the mean)
Mind the absolute value
64 – 58 = 88 – 64 = 64 – 40 = 64 – 60 =
72 – 64 = 66 – 64 = 80 – 64 = 64 – 48 =
Absolute Value
6 24 24 4
8 2 16 16
STEP 3
Find the average of the absolute values of the differences between each value in the data set and the mean.
= 12.5The mean absolute deviation is 12.5.
STEP 4 (DESCRIBE OR INTERPRET DATA)
This means that the average distance each data value is from the mean is 12.5 miles per hour.
YOUR TURN
The table shows speeds of ten birds. Find the mean absolute deviation of the data. Round to the nearest whole number. Describe what the mean absolute deviation represents.
What is the first Step?
Speeds of Top Ten Fastest Birds (mph)
88 77 65 70 65
72 95 80 106 68
STEP 1 FIND THE MEAN
=
=
The mean is 78.8
or 79
What is the next step?
STEP 2 FIND THE ABSOLUTE VALUE
Find the absolute value of the difference between each value in the data set and the mean. (How far each number or piece of data is from the mean.)
What is the next step?
Absolute Value
88 – 79 = 9 79 – 77 = 2 79 – 65 = 14
79 – 70 = 9 79 – 65 = 14
79 – 72 = 7 95 – 79 = 16
79 – 80 = 19
106 – 79 = 27
79 – 68 =11
STEP 3 FIND THE MEAN ABSOLUTE DEVIATIONFind the average of the absolute values of the differences
between each value in the data set and the mean.
=
12.2 or
The mean absolute deviation is 12