Question

Question 4
The following table gives the number of pages written by Sarika for completing her own book for 30 days.
$\begin{array}{cccccc}\text{Number of pages written per day}& 16-18& 19-21& 22-24& 25-27& 28-30\\ \text{Number of days}& 1& 3& 4& 9& 13\end{array}$
Find the mean number of pages written per day.

Answer 1

Since, given data is not continuous, we subtract 0.5 from the lower limit and add 0.5 in the upper limit of each class.

$\begin{array}{cccc}\text{Class mark}& Mid-value\left(x_i\right)& \text{Number of days}\left(f_i\right)& f_i{x}_i\\ 15.5-18.5& 17& 1& 17\\ 18.5-21.5& 20& 3& 60\\ 21.5-24.5& 23& 4& 92\\ 24.5-27.5& 26& 9& 234\\ 27.5-30.5& 29& 13& 377\\ \text{Total}& & 30& 780\end{array}$

$\therefore Mean\left(\overline{x}\right)=\frac{\sum f_i{x}_i}{\sum f_i}=\frac{780}{30}=26$
Hence, the mean of pages written per day is 26.