Question

if d means deviation ,what does it mean by u ?

Answer 1

Answer :

d basically used as : ​find the difference d_i between a and each of the x_i’s, that is, the deviation of ‘a’ from each of the x_i’s.

d = x - a

Here a = assumed mean

SO we use d in assumed mean method and d is our as a step to find the mean , by assumed mean method.

And

u_​i = $\frac{x_i-a}{h}$ ​where a is the assumed mean and h is the class size.

The method is used in the Step-deviation method. to find mean