
Introductory Econometrics 4th Edition by Jeffrey Wooldridge
Edition 4ISBN: 978-0324660609
Introductory Econometrics 4th Edition by Jeffrey Wooldridge
Edition 4ISBN: 978-0324660609 Exercise 5
Assume that the model y = X + u satisfies the Gauss-Markov assumptions and let
be the OLS estimator of . Let Z = G(X) be an n × (k + 1) matrix function of × and assume that Z X [a (k + 1) × (k + 1) matrix] is nonsingular. Define a new estimator of by
= (Z X)1Z y.
(i) Show that E(
X) , so that
is also unbiased conditional on X.
(ii) Find Var(
X). Make sure this is a symmetric, (k + 1) × (k + 1) matrix that depends on Z, X, and 2.
(iii) Which estimator do you prefer,
or
Explain
be the OLS estimator of . Let Z = G(X) be an n × (k + 1) matrix function of × and assume that Z X [a (k + 1) × (k + 1) matrix] is nonsingular. Define a new estimator of by
= (Z X)1Z y.(i) Show that E(
X) , so that
is also unbiased conditional on X.(ii) Find Var(
X). Make sure this is a symmetric, (k + 1) × (k + 1) matrix that depends on Z, X, and 2.(iii) Which estimator do you prefer,
or
ExplainExplanation
Given:
1) satisfies the Gauss-Markov as...
Introductory Econometrics 4th Edition by Jeffrey Wooldridge
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