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

$$\begin{array}{ccc}\text{Class Mark}& \text{Frequency}& f_i{x}_i\\ \text{30}& \text{12}& \text{360}\\ \text{40}& \text{16}& \text{480}\\ \text{50}& \text{17}& \text{850}\\ \text{60}& \text{15}& \text{900}\\ \text{70}& \text{8}& \text{560}\\ \text{80}& \text{19}& \text{1520}\\ \text{90}& \text{13}& \text{1170}\end{array}$$
$\sum f_i$=100
$\sum f_i{x}_i$ = 6000
Mean = $\frac{6000}{100}=60$