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ii.     It is not a quantitative measure of the relationship between the

                          variables. It is only a quantitative expression of the quantitative
                          change.
                   iii.   This method is not suitable in case of multiple correlation.


               Karl Pearson’s Coefficient of Correlation

               Actual Mean Method

                   Karl Pearson’s Method of measuring coefficient of correlation(r) : -


                       Prof. Karl-Pearson’s is a British Biometrician Who first advocate the
                       Product-moment method of measuring coefficient of correlation.

                                                                  (    )
                                                          =
                                                               ×      
                                                                


                                                                  (  −     )(  −  )
                                                        =                    2
                                                                (  −     ) 2 ×    (  −     )
                                                                              
                                                                     
                                                       =
                                                                 2
                                                                  ×     2


                                                   where    =    −              =    −   
               Example-1: - From the following data obtain Karl-Pearson’s coefficient of
               correlation by using actual mean method.


                     X             15             18             20              28             34
                     Y             40             42             46              50             52
                       Solution: - Karl Pearson’s coefficient of correlation.


                                                                          2
                                                                                       2

                  X         Y         =    −           =    −                                      ×   
                  15       40           -8               -6             64           36           48
                  18       42           -5               -4             25           16           20
                  20       46           -3               0               9            0            0
                  28       50           5                4              25           16           20
                  34       52           11               6              121          36           66

                                                                        2
                                                                                     2
                    =115        =230                                       =244         =104          =154



                  =       =  115  = 23                                      =       =  230  = 46
                           5                                                         5
                                                                  
                                                      =
                                                             2
                                                              ×     2
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