In: Statistics and Probability
Suppose we continue to randomly select letters with replacement from the set {A, B, C, D, E, F}. Let T = be the number of letters we need to collect in order to have both letter E and letter F at least once. For example, suppose we have a sequence of letters CAEEBDF EA · · · . Then T = 7 in the above sequence. (a) Find the pgf of T. (b) Use the pgf of T in (a) to find E(T) and Var(T). (c) Find P(T = k) for k ≥ 2.