1. Remove the observations for galaxies having leverage greater than 0.08 and refit the zero intercept model. What is the estimated age of the universe from this model?

2. Fit a quadratic regression model, that is, a model of the form

and plot the fitted curve and the simple linear regression fit on a scatterplot of the data. Which model do you consider more sensible considering the nature of the data? (The ‘‘quadratic model'' here is still regarded as a linear regression model since the term linear relates to the parameters of the model not to the powers of the explanatory variable.)