1. disjoint 2. many possibilities 3. no 4. false 5. dispersion 6. We see from (2.29)-(2.31) that P(R = 3, B <= 4) = 4/36 = 1/9 If we falsely assumed independence, we would have P(R = 3, B <= 4) = P(R = 3) P(B <= 4) Now P(B <= 4) = P(0 <= B <= 4) # key point! = P(B = 0) + P(B is in {1,2,3,4}) = 5/6 + P(R = 3 and B is in {1,2,3,4}) = 5/6 + P(R = 3) P(B is in {1,2,3,4} | R = 3) = 5/6 + (1/6) (4/6) = 34/36 = 17/18 So, our (wrong) answer would be (1/6) (17/18) = 17/108, about 0.157 7. same as 6, not counted 8. (2/6) 12 + (4/6) 1, about 4.67 9. Let S denote the square we are on after the first turn. Its support is 0,1,2,4,5,6,7, with associated probabilities a1 = (1/6) * (1/6) a2 = 1/6 + (1/6) * (1/6) 1/6 a2 = (1/6) + (1/6) * (1/6) a2 = (1/6) + (1/6) * (1/6) a2 = (1/6) + (1/6) * (1/6) a1 = (1/6) * (1/6) Var(S) = E(S^2) - (ES)^2 E(S^2) = a1 * 0^2 + a2 * 1^2 + (1/6) * 2^2 + a2 * 4^2 + a2 * 5^2 + a2 * 6^2 + a1 * 7^2 E(S) = a1 * 0 + a2 * 1 + (1/6) * 2 + a2 * 4 + a2 * 5 + a2 * 6 + a1 * 7 about 3.9 10. nochange <- function(c,r,k) (r^k)^(c-k) nochange(4,0.2,3) # about 0.008