Question

Question 2
Calculate the mean of the scores of 20 students in a mathematics test
$\begin{array}{cccccc}\text{Marks}& 10-20& 20-30& 30-40& 40-50& 50-60\\ \text{Number of students}& 2& 4& 7& 6& 1\end{array}$

Answer 1

We first, find the class mark $x_i$ of each class and then proceed as follows
$\begin{array}{cccc}\text{Marks}& Classmarks\left(x_i\right)& \text{Frequency}\left(f_i\right)& f_i{x}_i\\ 10-20& 15& 2& 30\\ 20-30& 25& 4& 100\\ 30-40& 35& 7& 245\\ 40-50& 45& 6& 270\\ 50-60& 55& 1& 55\\ & & \sum f_i=20& \sum f_i{x}_i=700\end{array}$
Therefore, $mean\left(\overline{x}\right)=\frac{\sum f_i{x}_i}{\sum f_i}=\frac{700}{20}=35$
Hence, the mean of scores of 20 students in mathematics test is 35.