Question

Find the mean of the following frequency distribution:

Class-interval:	0-10	10-20	20-30	30-40	40-50
No. of workers f:	7	10	15	8	10

Answer 1

Calculation of Mean

Class-interval	Mid-values ($x_i$	Frequency $f_i$	$d_i=x_i-25$	$u_i=\frac{x_i-25}{10}$	$f_i{u}_i$
0-10	5	7	-20	-2	-14
10-20	15	10	-10	-1	-10
20-30	25	15	0	0	0
30-40	35	8	10	1	8
40-50	45	10	20	1	20
		$N=\sum f_i=50$			$\sum f_i{u}_i=4$

WE have
A= 25, h= 10, N=50 and $\sum f_i{u}_i=4$
$\therefore Mean=A+h[\frac{1}{N}\sum f_i{u}_i]$
$\Rightarrow Mean=25+10\times \frac{4}{50}=25.8$