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Mean deviation is the mean of the distance between mean and each value in the given data.
Where,…… set of elements, is Mean and n stands for number of elements in the given data. Steps involved in finding the mean deviation
Find the mean for the given data
Find the absolute difference between each value and mean.
Find the sum of all values and then divide the result with number of numbers
Example 1: A student wrote 5 exams and secured 100 in Math, 84 in Science, 75 in English, 90 in Social and 96 in Biology. Find the mean deviation.
Find the mean:
= = = 89

µ 

  
= 100 
89 
100 – 89 = 11 
11 
= 84 
89 
84 – 89 = 5 
5 
= 75 
89 
75 – 89 = 14 
14 
= 90 
89 
90 – 89 = 1 
1 
= 96 
89 
96 – 89 = 7

7 



38 
Mean deviation = = = 7.6
Example 2: Find the missing number and mean deviation for the sample 4, 10, 15, 20, P, 2 and mean of the sample is 9.
Mean = =
9 =
Multiplying by 6 on both sides
51 + P = 54
Add – 51 on both sides
P = 3
So the missing number = P = 3

µ 

  
= 4 
9 
4 – 9 = 5 
5 
= 10 
9 
10 – 9 = 1 
1 
= 15 
9 
15 – 9 = 6 
6 
= 20 
9 
20 – 9 = 11 
11 
= P = 3 
9 
3 – 9 = 6

6 
= 2 
9 
2 – 9 = 7 
7 



36 
Mean deviation = = = 6