The ages (in years) of 50 students of a class in a school are given below:

Age (in years):	14	15	16	17	18
Numbers of students:	15	14	10	8	3

Find the mean age.

Calculation of Mean

xi	fi	fi xi
14	15	210
15	14	210
16	10	160
17	8	136
18	3	54
Total	$\sum _{}^{}{f}_i=$50	$\sum _{}^{}{f}_i{x}_i=$770

∴ Mean age = ​$\frac{\sum _{}^{}{f}_i{x}_i}{\sum _{}^{}{f}_i}=\frac{770}{50}=15.4\mathrm{yrs}$.