Question

In the formula $\overline{\mathrm{X}}=\mathrm{a}+\frac{\mathrm{\Sigma }{\mathrm{f}}_{\mathrm{i}}{\mathrm{d}}_{\mathrm{i}}}{\mathrm{\Sigma }{\mathrm{f}}_{\mathrm{i}}}$, for finding the mean of grouped data ${d_i}^{{\text{'}}^s}$ are derivations from $a$ of
(a) lower limits of classes (b) upper limits ofclasses
(c) mid-points of classes (d) frequency of the class marks

Answer 1

The given formula represents the formula to find the mean by assumed mean method.
Here, d_i = $x_i-a$ where x_i is the ith observation and a is assumed mean.
So, d_i's are the deviation from a of mid-points of the classes.
Hence, the correct answer is option (c).