1. How many degrees of freedom does the sample variance have when calculated from a sample of n observations? a. n b. n - 1 c. n + 1 d. none of the above 2. If X, Y, and Z are random variables and a and b are constants, then the expected value of Z = aX +bY is a. aE(X) - bE(Y) b. aE(X) + bE(Y) c. E(X) - E(Y) d. E(X) - E(Y) 3. The covariance between two random variables X and Y is a. E[(X - X)(Y- Y)] b. E(XY)2 - XY c. E(XY)2 - (XY)2 d. none of the above 4. If X is a normal random variable that has mean = 20 and standard deviation = 2, the standardized value of X = 16 is a. 4 b. -2 c. 2 d. -4 Solution 1. b 2. b 3. a 4. b (16-20)/2 = -2.