In: Statistics and Probability
Let X and Y have joint discrete distribution p(x, y) = 3 20 (.5 x ) (.7 y ), x = 0, 1, 2, . . . , and y = 0, 1, 2, . . .. Find the marginal probability function P(X = x). [hint: for a geometric series X∞ n=0 arn with −1 < r < 1, r 6= 0, then X∞ n=0 arn = a 1 − r ]