Question

Find the mean of the following data:

Frequency	20	35	52	44	38	31
Classes	0 – 20	20 – 40	40 – 60	60 – 80	80 – 100	100 – 120

Answer 1

C.I.	Frequency (fi)	xi	`bb(u_i = (x_i - a)/h)`	fiui
0 – 20	20	10	– 3	– 60
20 – 40	35	30	– 2	– 70
40 – 60	52	50	– 1	– 52
60 – 80	44	70 = a	0	0
80 – 100	38	90	1	38
100 – 120	31	110	2	62
	Σfi = 220			Σfiui = – 82

Let a = Assumed mean = 70,

Mean, `barx = a + (sumf_iu_i)/(sumf_i) xx h`

= `70 + ((-82))/220 xx 20`

= `70 - 82/11`

= 70 – 7.45

= 62.55