Question

Mean for the following frequency distribution table.

0-5	5-10	10-15	15-20	20-25	25-30
5	3	9	10	8	5

Answer 1

$Class$	$Class-mark$ $x_i$	$Frequency$ $f_i$	$f_i{x}_i$
$0-5$	$2.5$	$5$	$12.5$
$5-10$	$7.5$	$3$	$22.5$
$10-15$	$12.5$	$9$	$112.5$
$15-20$	$17.5$	$10$	$175$
$20-25$	$22.5$	$8$	$180$
$25-30$	$27.5$	$5$	$137.5$
		$\sum f_i=40$	$\sum f_i{x}_i=640$

$\overline{x}=\frac{\sum f_i{x}_i}{\sum f_i}=\frac{640}{40}=16$