(31) P(? )=|F(? )|, (32) (33) (34) (35) (36) P(? )=F*(? )G(? ).

Each pair of definitions involves an averaging process of some kind. In equation (28) there is an average over an ensemble of realizations; in equation (33), taking the limit as T? 8 is also a kind of averaging process. Only for ergodic processes are these two definitions exactly equivalent.