Question

Find mean by step-deviation method:

C.I.	63 – 70	70 – 77	77 – 84	84 – 91	91 – 98	98 – 105	105 – 112
Frequency	9	13	27	38	32	16	15

Answer 1

C.I.	Frequency  fi	Mid-value xi	A = 87.50  `bb(u_i = (x_i - A)/h)`	fiui
63 – 70	9	66.50	–3	–27
70 – 77	13	73.50	–2	–26
77 – 84	27	80.50	–1	–27
84 – 91	38	A = 87.50	0	0
91 – 98	32	94.50	1	32
98 – 105	16	101.50	2	32
105 – 112	15	108.50	3	45
Total	150			29

Here A = 87.50 and h = 7

`barx = A + h xx (sumf_iu_i)/(sumf_i)`

= `87.5 + 7 xx 29/150`

= 87.5 + 1.35

= 88.85