The total marks obtained by 40 students in the Annual examination are given below

Using step deviation method to find the mean of the above data.

In step deviation method, we divide deviation by the width of the class intervals in order to simplify the calculation.

Here, we shall assume a mean from the given x_i’s. Let the assumed mean (A) be 325.

Also,

Where, A = assumed mean = (here) 325

& c = width of the class intervals = (here) 50

Construct the following table:

Using these values, we can find the arithmetic mean of the following data.

Arithmetic mean is given by

⇒

⇒

⇒ Mean = 326.25

Thus, arithmetic mean of the following data is 326.25.