•     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
•     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