Question

Find the mean for the following data.

$$\begin{array}{cccccc}Class& 0-20& 20-40& 40-60& 60-80& 80-100\\ Frequency& 5& 11& 12& 13& 9\end{array}$$

Answer 1

$$\begin{array}{ccc}\text{Class Mark}& \text{Frequency}& f_i{x}_i\\ \text{10}& \text{5}& \text{50}\\ \text{30}& \text{11}& \text{330}\\ \text{50}& \text{12}& \text{600}\\ \text{70}& \text{13}& \text{910}\\ \text{90}& \text{9}& \text{810}\end{array}$$
$\sum f_i$=50
$\sum f_i{x}_i$ = 2700
Mean = $\frac{2700}{50}=54$