Question

Find the mean of the following distribution using assumed mean.

$$\begin{array}{cccccc}ClassInterval& 100-110& 10-120& 120-130& 130-140& 140-150\\ Frequency& 6& 9& 14& 2& 19\end{array}$$

Answer 1

Let the assumed mean be 125.

$$\begin{array}{cccc}{x}_i& f_i& d_i& f_i{d}_i\\ \text{105}& \text{6}& \text{-20}& \text{-120}\\ \text{115}& \text{9}& \text{-10}& \text{-90}\\ \text{125}& \text{14}& \text{-0}& \text{0}\\ \text{135}& \text{2}& \text{10}& \text{20}\\ \text{145}& \text{19}& \text{20}& \text{380}\end{array}$$
$\sum f_i$=50
$\sum f_i{d}_i$ = 190
Mean = $125+\frac{190}{50}=128.8$