Prof. Bryan Caplan

http://www.gmu.edu/departments/economics/bcaplan

Spring, 1998

Econometrics Pre-Test Answers

Here are the answers for the Pre-Test. If you missed 4 or more of the questions correct, you should begin an intensive review of this material: it will get harder in week 3. If you missed 2-3 questions, you may want to spend a few hours in extra review. If you missed 0-1 questions, you will probably be well-prepared for this class.

Find E(X), E(X^{2}), Var(X), and SD(X), where X is:

1. A random variable that is equal to 0 25% of the time, 1 50% of the time, 2 20% of the time, and 10 5% of the time.

E(X)=1.4 E(X^{2})=6.3 Var(X)=4.34 SD(X)=2.083

Evaluate the following expressions:

1. 2.

Determine the Probability of the Following Events:

1. P(*X*<5|*X+Y*=8)=1/3 2. P(*X+Y>*4|*X<5*)=.625

Evaluate the Following Expressions:

- XY=
- X'-Y=
- rank()=1 (second column equals 3*first column)
- (XY)
^{-1}=