Question

The following table shows the weight of 12 students:

Weight in kg.	67	70	72	73	75
Number of students	4	3	2	2	1

Find the Mean weight.

Answer 1

Let the assumed mean A = 72. Calculate of Mean:

Weight in kgs.	Number of students `(f_i)`	`d_i = x_i  - A = x_i - 72`	`f_i d_i`
67	4	-5	-20
70	3	-2	-6
72	2	0	0
73	2	1	2
75	1	3	3
	N = `sumf_i = 12`		`sumf_i d_i = -21`

We have,
N = 12, E = `f_i d_i` = -21, A = 72
Mean = `"A" + (1)/"N" (sumf_i d_i)`
= `72 + (-21/12)`
= `72 - (7)/(4)`
= `(288 - 7)/(4)`
= `(2881)/(4)`
= 70·25 kgs.
∴ Mean weight = 70·25 kgs.