Data and Packages:

We use the dataset "smoking.csv". We are interested in estimating the smoking probability as a function of age. For all estimation of linear probability models, the type of standard error should be "HC1" or equivalently "stata".

For the questions below, it is assumed that the required R-packages are loaded and the data are attached.

QUESTION 4 Regress smoker on quadratic polynomials of age, using a probit regression and find the p-value for testing the hypothesis that the z-value is linear in age. (two decimal places)