9. What happens in the quadratic model for cars that are very old? Can you think of a plausible "real world" explanation for this- or is it a flaw of the quadratic model?

10. Would the fit improve significantly if you also included a cubic term? Justify your answer.

Model #3: Complete second order model

11. Write down the complete second order model for predicting a used car price based on ageand mileage. Note: This is model before estimating the fit, so use general coefficients (or Bi if you can't type a beta).

12. Use R to estimate the coefficients in this model. Include the summary and anova output and write down the fitted prediction equation with good statistical notation.

13. Show the details of a nested F-test for the importance of just the second order terms (quadratic and interaction) that involve mileage in this model. Include the output needed to get the information to complete the test. Show all the usual details (hypotheses, test statistic, p-value and an informative conclusion in context). In particular, show how the test statistic is computed by putting values into a formula (although you may confirm the result with R).

Wrap-up: Based on the various models you have considered for predicting the price of a used car, which would you recommend using in practice?Give some justification for your answer. 9. What happens in the quadratic model for cars that are very old? Can you think of a plausible "real world" explanation for this- or is it a flaw of the quadratic model?

10. Would the fit improve significantly if you also included a cubic term? Justify your answer.

Model #3: Complete second order model

11. Write down the complete second order model for predicting a used car price based on ageand mileage. Note: This is model before estimating the fit, so use general coefficients (or Bi if you can't type a beta).

12. Use 9. What happens in the quadratic model for cars that are very old? Can you think of a plausible "real world" explanation for this- or is it a flaw of the quadratic model?

10. Would the fit improve significantly if you also included a cubic term? Justify your answer.

Model #3: Complete second order model

11. Write down the complete second order model for predicting a used car price based on ageand mileage. Note: This is model before estimating the fit, so use general coefficients (or Bi if you can't type a beta).

12. Use R to estimate the coefficients in this model. Include the summary and anova output and write down the fitted prediction equation with good statistical notation.

13. Show the details of a nested F-test for the importance of just the second order terms (quadratic and interaction) that involve mileage in this model. Include the output needed to get the information to complete the test. Show all the usual details (hypotheses, test statistic, p-value and an informative conclusion in context). In particular, show how the test statistic is computed by putting values into a formula (although you may confirm the result with R).

Wrap-up: Based on the various models you have considered for predicting the price of a used car, which would you recommend using in practice?Give some justification for your answer. to estimate the coefficients in this model. Include the summary and anova output and write down the fitted prediction equation with good statistical notation.

13. Show the details of a nested F-test for the importance of just the second order terms (quadratic and interaction) that involve mileage in this model. Include the output needed to get the information to complete the test. Show all the usual details (hypotheses, test statistic, p-value and an informative conclusion in context). In particular, show how the test statistic is computed by putting values into a formula (although you may confirm the result with R).

Wrap-up: Based on the various models you have considered for predicting the price of a used car, which would you recommend using in practice?Give some justification for your answer.