17. Exemplar Exercise problem II

 1. If $x_i$’s are the mid points of the class intervals of grouped data, $f_i$’s are the corresponding frequencies and $\overline x$ is the mean, then $\sum(f_ix_i- \overline x)$  is equal to

 

 

 

2. In the formula $\overline x=a+h\frac{\sum f_iu_i}{\sum f_i}$ for finding the mean of grouped frequency distribution, $ui=$