Consider the sample regression Y i = 1 + 2 X i + u i
Question:
Consider the sample regression
Yi = β̂1 + β̂2Xi + ûi
Imposing the restrictions (i) Σûi = 0 and (ii) Σ ûiXi = 0, obtain the estimators β̂1 and β̂2 and show that they are identical with the least-squares estimators given in Eqs. (3.1.6) and (3.1.7). This method of obtaining estimators is called the analogy principle. Give an intuitive justification for imposing restrictions (i) and (ii). (Hint: Recall the CLRM assumptions about ui.) In passing, note that the analogy principle of estimating unknown parameters is also known as the method of moments in which sample moments (e.g., sample mean) are used to estimate population moments (e.g., the population mean). As noted in Appendix A, a moment is a summary statistic of a probability distribution, such as the expected value and variance.
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