4.For random variables X and Y, and constants a, b, and c: E(a+bX+cY)=
A.shows that at least basic statistical techniques (estimation; confidence intervals) remain accurate even when assumptions are violated in finite samples.
B. can be empirically tested, if not mathematically proved.
C. helps us approximate finite-sample properties.
D. is useful only if we plan to continue gathering more and more data in the future.
6.Let X be a random variable measuring pre-tax earnings in dollars, and let after-tax earnings Y be the function Y = $2000 + 0.8 X. If E(X)=$50,000 and Var(X)=4×108dollars2, then what is the mean after-tax earnings?
7.Let Z be a random variable with a standard normal distribution, N(0,1). What is P(Z<0)?
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