Find the missing frequency, if mean is 62.

C.I 0-40 40-80 80-120 120-160

Frequency 6 9 ? 2

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Solution

C.I.
Mid-Point
(m) Frequency
(f) fm

0 − 40
40 − 80
80 − 120
120 − 160 20
60
100
140 6
9
? (f)
2 120
540
100f
280

Σf = 17+f Σfm = 940+100f

$X = 62 X = \frac{Σ f m}{Σ f} 62 = \frac{940 + 100 f}{17 + f} 1054 + 62 f = 940 + 100 f 38 f = 114 f = \frac{114}{38} = 3$
Thus, the missing freuency is 3.

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Similar questions

Class	0-40	40-80	80-120	120-160	160-200
Frequency	12	20	35	30	23

Class	0 − 20	20 − 40	40 − 60	60 − 80	80 − 100	100 – 120	120 – 140
Frequency	6	8	10	12	6	5	3

Class-interval	20−40	40−60	60−80	80−100	100−120	120−140	140−160
Frequency	3	7	11	15	13	6	2

Calculate the Mean Deviation using mean and Standard Deviation for the following distribution.

Class	0-20	20-40	40-60	60-80	80-100	Total
Frequency	17	f₁	32	f₂	19	120

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