Multiple Choice
Consider the following simple regression model y = 0 +
1x1 + u. Suppose z is an instrument for x. Which of the following statements is true?
A) The condition Cov(z,u) = 0 can be tested statistically.
B) The condition Cov(z,x) 0 cannot be tested statistically.
C) The instrumental variables estimator is always biased if Cov(x,u) 0.
D) The ordinary least squares estimator is unbiased if Cov(x,u) 0 .
Correct Answer:

Verified
Correct Answer:
Verified
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