=+system o, and let C, be the w-set where every k-tuple of + 1's (k arbitrary)

occurs in Y(" )(w), Y2)

(c) ,... with the right asymptotic relative frequency (in the sense of Problem 6.12). Let C be the intersection of C ,, over all effective selection systems o. Show that C lies in $ (the o-field in the probability space

(0, 9, P) on which the X ,, are defined) and that P(C)= 1. A sequence