Statistics – Notes

Mean of Grouped Data

Mean of given set of data is given by the sum of values of all the given observations divided by the number of observations.

The three ways of finding the mean of grouped data are:

• Direct Method
• Assumed Mean Method
• Step-Deviation Method

Class Mark (x_i)

Using direct method, Mean  =   when x_i’s are mid values

Using assumed mean method, = a +  where a = assumed mean and d_i = x_i-a

Using step deviation method,  = a + h , where a = assumed mean,

h = class size and u_i