6. What is the sampling variation of the OLS estimator?

7. What do we mean when we say that an estimator is unbiased?

8. What do we mean when we say that an estimator is efficient?

9. In the context of the classical linear regression model, which assumptions need to be satisfied to ensure that the OLS estimator is unbiased and efficient?

10. What does the error term represent in the classical linear regression model?