1. Load the AER() package and tute8_smoke.csv into R. Construct three new variables in your dataset:

nprevisit_sq=nprevisit X nprevisit

nprevisit_cu=nprevisit X nprevisit X nprevisit

nprevisit_qu=nprevisit X nprevisit X nprevisit X nprevisit

Using sequential hypothesis testing, determine the order of the polynomial in a non-linear regression where the dependent variable birthweight is a polynomial function of nprevisit. What is the order of the polynomial that sequential hypothesis testing yields? Ensure that you allow for heteroskedasticity-robust standard errors in conducting your tests.

2. Working with the polynomial regression you estimated as part of question 2 of Quiz 11, based on the estimated regression function relating birthweight to nprevisit, what is the partial effect of changing nprevisit from 2 to 6 on birthweight?