2. Calculate Mean deviation, Coefficient of M.D. from the following grouped data

X	Frequency
10	3
11	12
12	18
13	12
14	3

Solution:
Mean deviation :

`x` `(1)`	`f` `(2)`	`f*x` `(3)=(2)xx(1)`	`|x-bar x|=|x-12|` `(4)`	`f*|x-bar x|` `(5)=(2)xx(4)`
10	3	30	2	6
11	12	132	1	12
12	18	216	0	0
13	12	156	1	12
14	3	42	2	6
---	---	---	---	---
--	`n=48`	`sum f*x=576`	--	`sum f*|x-bar x|=36`

Mean `bar x=(sum f x)/n`

`=576/48`

`=12`

Mean deviation of Mean
`delta bar x = (sum f*|x - bar x|)/n`

`delta bar x = 36/48`

`delta bar x = 0.75`


Coefficient of Mean deviation `=(delta bar x)/(bar x)`

`=0.75/12`

`=0.0625`

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