Question

Find the mean of the following data.

$$\begin{array}{cccccc}Class& 0-10& 10-20& 20-30& 30-40& 40-50\\ Frequency& 6& 7& 11& 9& 7\end{array}$$

Answer 1

$$\begin{array}{ccc}\text{Class Mark}& \text{Frequency}& f_i{x}_i\\ \text{15}& \text{6}& \text{90}\\ \text{25}& \text{7}& \text{175}\\ \text{35}& \text{11}& \text{385}\\ \text{45}& \text{9}& \text{405}\\ \text{55}& \text{7}& \text{385}\end{array}$$
$\sum f_i$=40
$\sum f_i{x}_i$ = 1440
Mean = $\frac{1440}{40}=36$