In the formula $\bar{x}= a+\frac{\sum f_{i}d_{i}}{\sum f_{i}}$ for finding the mean of grouped data di’s are deviations from (A) lower limits of the classes (B) upper limits of the classes (C) mid points of the classes (D) frequencies of the class marks

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.
We know that di = xi – a
where xi is data and a is mean
So, di are the derivative from mid-point of the classes.