STATISTICS OVERVIEW (MEAN)

THERE ARE THREE  TYPES OF SERIES-
1.INDIVIDUAL SERIES
-   Let x1, x2.....................xn be given obs. and 'n' be the total no. of obs.,then  
mean = Σxi/n

 where xi is sum of all obs.

                                                                                                                                                                                                                                   

2.DISCRETE SERIES

-   Let x1,x2..........xn be given obs. and f1,f2.....fn be their frequencies then 

mean= Σfixi/Σfi

3.CONTINUOUS SERIES

-  Continuous series means when class intervals are given.

Mean can be found by three methods here-

(A)DIRECT METHOD

When upper and lower limits of the class intervals are small.

mean=Σfixi/Σfi 

(B)DEVIATION OR ASSUMED MEAN METHOD

When upper and lower limits of the class intervals are large,then this method is used.

the assumed mean is taken from class mark(xi)

mean= A + Σfidi/Σfi, where d = mean – A, where A is the assumed mean.

(C)STEP DEVIATION METHOD

This method is used to make the calculations for finding the mean easy.

Mean= A + (Σfiui/Σfi)h, where A is the assumed mean and u = di/h.

NOTE- Step Deviation method is used mainly for finding the mean when data is given in the continuous series with large value of upper and lower limits.We can use the other two methods if they are specified in the question or according to the conditions of the questions.