State whether the following statements are correct or not in the context of regression analysis, and explain why:
a. The sum of OLS residuals is zero.
b. The OLS estimator of b0 of the regression equation y = b0 + u is the sample mean of y.
a.
Correct.
Reason: OLS method provides mean value of Y for a given X i.e. E(Y|X). When all deviations are summed up, errors are summed up in following way:
Sum(ei) = Sum(Y - E(Y|X)) = 0
b.
Correct.
As I presented in part a, conditional means of Y are calculated when X is present.
In this case (absence of X), only unconditional mean of Y is calculated which is also known as sample mean.
State whether the following statements are correct or not in the context of regression analysis, and...
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