Consider an urn containing four balls: a yellow ball with the number 1 on it, a
ID: 3262618 • Letter: C
Question
Consider an urn containing four balls: a yellow ball with the number 1 on it, a red ball with the number 1 on it, a yellow ball with the number 2 on it, and a red ball with the number 2 on it. Suppose that two of these balls wil be randomly drawn from the urn. Letting X be the absolute value of the dierence of the numbers on the two balls (so X can only assume the values 0 (if the two balls have the same number on them) and 1 (if the two balls have dierent numbers on them)) and letting Y be the number of colors obtained (so Y can only assume the values 1 (if the two balls are the same color) and 2 (if the balls are dierent colors)), give the joint pmf of X and Y, using a tabular form similar to that used in Problem 1 on p. 342 of the text.
Explanation / Answer
ley y1 = yellow ball with number 1
y2 = yellow ball with number 2
r1 = red ball with number 1
r2 = red ball with number 2
sample space = { y1y2, y1r1, y1r2,y2r1,y2r2,r1r2}
P(0,1) = 0
P(0,2) = 1/6 + 1/6 = 1/3
P(1,1) = 1/6 + 1/6 = 1/3
P(1,2) = 1/3
joint PMF is
0
x/y 1 20
0 1/3 1 1/3 1/3