4.4 Given the following equations =3638.25 - 0.148 torwrk -11.13 educ +2.20 age (112.28) (0.17) (5.88) (1.45) n=706 R-=0.113 Dropping educ and age from the equations gives: deep = 3.58638 -.151 ford (38.91) (017) n = 706, R = .103. i. Are educ and age jointly significant in the original equation at the 5% level? Justify your answer. [5] in. Does including educ and age in the model greatly affect the estimated tradeoff between sleeping and working? [2] iii. Suppose that the sleep equation contains heteroskedasticity. What does this mean about the tests computed in parts (i) and (ii)? (2] Good luck