12.80 You have been asked to develop a multiple regression model to predict the traffic fatality rate per 100 million miles in 2007. The data file Vehicle Travel State contains traffic data by state for the year 2007; the variables are described in the Chapter 11 appendix.

Consider the following possible predictor variables and select only those that are conditionally significant; per capita disposable income, percent of population in urban areas, total licensed drivers, total motor vehicle registrations, percent interstate highway miles, motor vehicle fuel tax in cents per gallon, total highway expenditure divided by number of licensed drivers, doctors per 1,000 population, nurses per 1,000 population, and Medicaid enrollment as a fraction of total population.