#### In the formula $\bar{x}= a+h\left ( \frac{\sum f_{i}u_{i}}{\sum f_{i}} \right )$ for finding the mean of grouped frequency distribution, ui = (A) $\frac{x_{i}+a}{h}$           (B) h(xi – a)                 (C) $\frac{x_{i}-a}{h}$                  (D) $\frac{a-x_{i}}{h}$

Solution.    Mean: It is the average of the given numbers/observations. It is easy to calculate mean. First of all, add up all the observations and then divide by the total number of observations.
Also we know that di = xi – a  and  $u_{i}= \frac{d_{i}}{h}$
$u_{i}= \frac{d_{i}}{h}$
put       di = xi – a
$u_{i}= \frac{x_{i}-a}{h}$
Hence option C is correct