Page 104 - Introduction to Statistical Pattern Recognition
P. 104

86                         Introduction to Statistical Pattern Recognition




                        0’  =E [{ h (X) -   IO;]

                           = E[( (M2 - MI)Y(X - M;)]2 I Oil

                           = (M2 - M1)YE{(X - M,)(X - M;)T IO; }X4(M2 - MI)

                           = (M* - M1)Y(M* - MI) = 2q .                            (3.99)
                       The above holds because E { (X - Mj)(X - Mi)‘  IO,  ]  is Z,  (=Z),  as was shown
                       in (2.13).
                            Figure 3-15  shows the density functions of  h(X) for o1 and y, and the



















                       Fig. 3-15  Density functions of  h(X) for normal distributions with  equal co-
                                 variances.


                       hatched parts correspond to the error probabilities which are due to the Bayes
                       test for minimum error.  Therefore,


                                                                                  (3.100)


                                                                                  (3.101)


                       where a(.) is the normal error function of (3.39), and
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