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Unit 6: Measures of Central Tendency




          Remarks:  If  the most  repeated values,  in the above  analysis  table, were  not  adjacent,  the  Notes
          distribution would have been bi-modal, i.e., having two modes.


                 Example: The monthly profits (in  ) of 100 shops are distributed as follows:
               Profit per Shop : 0 -100 100 - 200 200 - 300 300 - 400 400 - 500 500 - 600
                No. of Shops  :  12     18       27       20       17        6
          Determine the 'modal value' of the distribution graphically and verify the result by calculation.
          Solution:
          Since the distribution is regular, the modal class would be a class having the highest frequency.
          The modal class, of the given distribution, is 200 - 300.
          Graphical Location of Mode
          To locate mode we draw a histogram of the given frequency distribution. The mode is located as
          shown in Figure.
                                 Figure  6.1:  Graphical  Location of  Mode
















          From the figure, mode =   256.
          Determination of Mode by interpolation formula
          Since the modal class is 200 – 300, L  = 200,    1  = 27 – 18 = 9,    2   = 27 – 20 = 7 and h = 100.
                                      m
                            9
                 M  = 200 +     100 =   256.25
                   o       9 7

          6.5.2 Merits and Demerits of Mode

          Merits
          1.   It is easy to understand and easy to calculate. In many cases it can be  located just  by
               inspection.
          2.   It can be located in situations where the variable is not measurable but categorisation or
               ranking of observations is possible.
          3.   Like mean or median, it is not affected by extreme observations. It can be calculated even
               if these extreme observations are not known.
          4.   It can be determined even if the distribution has open end classes.
          5.   It can be located even when the class intervals are of unequal width provided that the
               width of modal and that of its preceding and following classes are equal.
          6.   It is a value around which there is more concentration of observations and hence the best
               representative of the data.



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