Prof. Bryan Caplan

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(X2), 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(X2)=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:

  1. XY=
  2. X'-Y=
  3. rank()=1 (second column equals 3*first column)
  4. (XY)-1=