Question

Calculate mean form the following data:

X	0−10	10−20	20−30	30−60	60−90
Frequency	5	9	20	12	4

Answer 1

Class Interval	Mid-Values (m)	(f)	fm
0 − 10 10 − 20 20 − 30 30 − 60 60 − 90	5 15 25 45 75	5 9 20 12 4	25 135 500 540 300
		$\mathit{\Sigma }\mathit{f}$=50	$\mathit{\Sigma }\mathit{f}\mathit{m}$=1500

Calculating the mean using direct method:

$$\begin{gathered} \overline{\mathit{X}}=\frac{\Sigma fm}{\Sigma f} \\ or,\overline{X}=\frac{1500}{50} \\ \Rightarrow \overline{X}=30 \end{gathered}$$

Hence, mean of the above series is 30