Mean Absolute Deviation

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Mean Absolute Deviation - PowerPoint PPT Presentation

Mean Absolute Deviation. Vocabulary. Deviation: The distance that two points are separated from each other. Deviation from the mean : How far the data point is from the mean. To find this distance, subtract the two values (the data point and the mean).

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Mean Absolute Deviation

Vocabulary
• Deviation: The distance that two points are separated from each other.
• Deviation from the mean: How far the data point is from the mean. To find this distance, subtract the two values (the data point and the mean).
• Mean absolute deviation (MAD): the average distance of all the data points from their mean. This will tell you how spread out your data is around the mean.
Example 1

Find the mean absolute deviation of the following test scores:

87, 94, 72, 65, 97, 77

87, 94, 72, 65, 97, 77

87

94

72

65

97

77

Step 1: Write the data in the first column of the table.

87, 94, 72, 65, 97, 77

87

94

72

65

97

+ 77

492 ÷ 6 = 82

87

94

72

65

97

77

82

82

82

82

82

82

Step 2: Calculate the mean of the data and write that in each cell of column 2.

87, 94, 72, 65, 97, 77

-5

-12

10

17

-15

5

87

94

72

65

97

77

82

82

82

82

82

82

82 – 87 = -5

82 – 94 = -12

82 – 72 = 10

82 – 65 = 17

82– 97 = -15

82 – 77 = 5

Step 3: Subtract column 1 from column 2 and write the difference in column 3.

87, 94, 72, 65, 97, 77

-5

-12

10

17

-15

5

5

12

10

17

15

5

87

94

72

65

97

77

82

82

82

82

82

82

Step 4: Rewrite all the numbers from column 3 as positive numbers in column 4 (Absolute Value).

87, 94, 72, 65, 97, 77

-5

-12

10

17

-15

5

64÷ 6

= 10.7

5

12

10

17

15

5

87

94

72

65

97

77

82

82

82

82

82

82

64

6

10.7

Step 5: Calculate the mean of the data in column 4, and you’re done! This is the MAD.

Example 2