... KÞ1=2½‘‘seð^bbjÞ’’=^ss2=ð^mmjÞ1=2 5: 35 Many econometrics packages compute equation (5. 35) for you, but it is also easy tocompute directly. Chapter 51 00 5. 5. One occasionally sees the following ... estimated in Example 5. 5, where actual educa-tion, say educÃ, plays the role of xÃK. Use IQ as the indicator of q ¼ ability, and KWW, meduc, feduc, and sibs as the elements of z. 5. 9. Suppose that ... 300,000 to 50 0,000 observations! The problem is that the instruments—representing quarters of birth and various interactions of these with year of birth and state of birth—are very weak, and they...