Question

The following table given the weekly wages (in Rs.) of workers in a factory:

Weekly wages (in Rs.)	$50-55$	$55-60$	$60-65$	$65-70$	$70-75$	$75-80$	$80-85$	$85-90$
No. of workers	$5$	$20$	$10$	$10$	$9$	$6$	$12$	$8$

Calculate:
The mean.

Answer 1

$Weeklywages$	$Class-mark$ $x_i$	$No.ofworker$ $f_i$	$f_i{x}_i$
$50-55$	$52.5$	$5$	$262.5$
$55-60$	$57.5$	$20$	$1150$
$60-65$	$62.5$	$10$	$625$
$65-70$	$67.5$	$10$	$675$
$70-75$	$72.5$	$9$	$652.5$
$75-80$	$77.5$	$6$	$465$
$80-85$	$82.5$	$12$	$990$
$85-90$	$87.5$	$8$	$700$
		$\sum f_i=80$	$\sum f_i{x}_i=5520$

$\Rightarrow$ Required mean $=\frac{\sum f_i{x}_i}{\sum f_i}=\frac{5520}{80}=69$