Mathematics

For data given in the adjoining table, the mean is :
C.I. f x u = (x - A)/i f × u
0-10 5
10-20 10
20-30 10
17
27
25
60

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In the table,

x is the mean value or class mark,

i = class-size = 10,

C.I.	f	x	u = (x - A)/i	f × u
0-10	5	5	(5 - 15)/10 = -10/10 = -1	-5
10-20	10	A = 15	(15 - 15)/10 = 0/10 = 0	0
20-30	10	25	(25 - 15)/10 = 10/10 = 1	10
Total	Σf = 25			Σfu = 5

By formula,

Mean = A + $\dfrac{Σfu}{Σf} \times i$

Substituting values we get :

Mean = 15 + $\dfrac{5}{25} \times 10 = 15 + \dfrac{50}{25}$ = 15 + 2 = 17.

Hence, Option 1 is the correct option.

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