Question

Find the mean of the following data, using direct method:

Class	25-35	35-45	45-55	55-65	65-75
Frequency	6	10	8	12	4

Answer 1

Class	Frequency`(f_i)`	Mid values`(x_i)`	`(f_i xx x_i)`
25-35	6	30	180
35-45	10	40	400
45-55	8	50	400
55-65	12	60	720
65-75	4	70	280
	∑`f_1 = 40`		`∑ (f_i xx x_i)=1980`

∴ Mean , x  = `(∑ (f_i xx x_i)) /(∑f_1)`

  =`1980/40`

  =49.5

  ∴ x = 49.5