16 Refer to the previous exercise. and use software to obtain regression diagnostics

a) Based on hat values and studentized esiduals, does it seem as if any observations may be influential? Explain.

b) Study the DFFITS values Which, if any, observations have a strong influence on the fitted values?

c) Study the DFBETAS values. For each predictor, which if any observations have a strong influence on the parameter estimates?

d) Remove the observation that seems most influential to you, and refit the model. Is the fit different in any substantive way?