R.1 A random variable X is defined to be the difference between the higher value and the lower value when two dice are thrown. If they have the same value, X is defined to be zero. Find the probability distribution for X.
R.3 Find the expected value of X in Exercise R.1.
R.6 Calculate E(X²) for X defined in Exercise R.1.
R.9 Calculate the population variance and the standard deviation of X as defined in Exercise R.1., using the definition given by equation (R.8) in the textbook.
R.11 Using equation (R.9) in the textbook, find the variance of the random variable X defined in Exercise R.1. and show that the answer is the same as that obtained in R.9. (Note: You have already calculated E(X) in R.3 and E(X²) in R.6.)
R.13 Suppose a variable Y is an exact linear function of X: Y = λ + μX where λ and μ are constants. Demonstrate that the correlation between X and Y is equal to 1 or –1, according to the sign of μ. (This question is different from R.13 in the third edition text)
Note: (R.8): var(X)=E[(X – μx)²] and when X is discrete, it is equal to Σⁿᵢ₌₁(xᵢ – μx)²pᵢ
(R.9): var(X)=E(X²)– μ²x