Question

The following table gives the age of 50 student of a class. Find the arithmetic mean of their ages. 

Age-years	16 – 18	18 – 20	20 – 22	22 – 24	24 – 26
No. of students	2	7	21	17	3

Answer 1

Age in years C.I.	`x_i`	Number of student (`f_i`)	`x_i f_i`
16 – 18	17	2	34
18 – 20	19	7	133
20 – 22	21	21	441
22 – 24	23	17	391
24 – 26	25	3	75
Total		50	1074

`barx = (f_ix_i)/(sumf)`

= `1074/50`

= 21.48