Question

Find the mean of the following frequency distribution by the short cut method : 

Class	0-10	10-20	20-30	30-40	40-50
Frequency	9	12	15	10	14

Answer 1

Class Interval	xi	fi	A = 25 d = x - A	${\displaystyle f_{i}d}$
0-10	5	9	-20	-180
10-20	15	12	-10	-120
20-30	A = 25	15	0	0
30-40	35	10	10	100
40-50	45	14	20	280
Total		60		80

${\displaystyle \overline{x}=A+\frac{\Sigma f_{i}d}{\Sigma f_i}}$

${\displaystyle \overline{x}=25+\frac{80}{60}}$

${\displaystyle \overline{x}=25+1.33}$

${\displaystyle \overline{x}=26.33}$

${\displaystyle \therefore }$ Mean = 26.33