Question

(b) The joint probability mass function for a pair of discrete (integer-valued) random variables X and Y is Px,y(n, m) = 60 ), nm > 0, 70. no () Find the marginal mass functions of X and Y. Pyin) (ii) Are X and Y independent? Justify your answer. (iii) Show that the probability mass function for X + Y is Otherwise. y Px(n) = < 3 (3), 720 Sinzo ), náo. [4] (ii) Show and y indepens functions Px+v(n) = { (3) - n20, otherwise.