In Appendix D, Table D.3, we show data taken from records of the number of licensed vehicles and the number of fatalities in the United States for the years 1950 through 1979. Here NOV is the number of vehicles x 10, and FATAL is the number of fatalities x 10 Fit the simple linear model FATAL +NOV+e. Complete the parameter estimation and 40' tables. Fit the quadratic model FATAL B+ BNOV + BNOV + in both uncentered and centered form. Interpret the coefficients in these two models.

e. Examine the plot of residuals against predicted values for the linear model. How might you explain the features of this plot for both low and high values of NOP? Recall that prior to 1974 the speed limit was 65 mph but was reduced to 55 mph for the last five years of this study. Does the quadratic model adequately address this change?