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, \(ui=\)