Question

The following table shows the weight of $30$ students in a class.

Weight (in $kg$)	$35$	$36$	$37$	$38$	$39$	$40$
Number of students	$4$	$2$	$8$	$2$	$5$	$9$

Find the mean weight of the students.

Answer 1

Finding the mean weight of the students:

Mean $=\frac{{\displaystyle \sum _i}{f}_i{x}_i}{{\displaystyle \sum _i}{f}_i}$

Total number of students $=\sum _i{f}_i=30$

Weight $\left(x_i\right)$	Frequency $\left(f_i\right)$	$f_i{x}_i$
$35$	$4$	$35\times 4=140$
$36$	$2$	$36\times 2=72$
$37$	$8$	$37\times 8=296$
$38$	$2$	$38\times 2=76$
$39$	$5$	$39\times 5=195$
$40$	$9$	$40\times 9=360$

$\sum _i{f}_i{x}_i=140+72+296+76+195+360=1139$

Mean weight $=\frac{1139}{30}=37.9$

Thus, the mean weight of the students is $37.9kg$.