C6.7 Use the data in ATTEND.RAW for this exercise. (i) In the model of Example 6.3, argue that stndfnl/ priGPA  2  24priGPA  6atndrte.

Use equation (6.19) to estimate the partial effect when priGPA
2.59 and atndrte
82. Interpret your estimate. (ii) Show that the equation can be written as stndfnl
0  1atndrte  2priGPA  3ACT  4(priGPA  2.59)2  5ACT2  6 priGPA(atndrte  82)  u, where 2
2  24(2.59)  6(82). (Note that the intercept has changed, but this is unimportant.) Use this to obtain the standard error of ˆ 2 from part (i). (iii) Suppose that, in place of priGPA(atndrte82), you put (priGPA2.59)  (atndrte  82). Now how do you interpret the coefficients on atndrte and priGPA?