Statistics-Notes

•     Lets remember that the mean, mode and median are measures if central tendency ie numerical representatives of the given data.

•     Class mark= upper limit + lower limit

                                               2

•     Mean of the grouped data

        1.   Using direct method:

        2.   Using assumed mean method::

                    

        3.   Using step deviation method:

•     The mode of the grouped data is

         Mode: l + ( f₁–f₂/ 2f₁–f₀–f₂)x h

         Where, l= lower limit of the class

                           h= size of the class

                           f₁= frequency of the modal class

                           f₀= frequency of the preceding class

                           f₂= frequency of the succeeding class

•     The cumulative frequency of a class is the frequency obtained by adding the frequencies of all the class preceding the given class.

•     Median if the grouped data

         Median= l + (n/2–cf/ f) X h

         Where, l= lower limit of median class

         n = number of observations

         c f= cumulative frequency of the class preceding the median class

         f= frequency of median class

         h= class size