Refit the quadratic regression model assuming Var(Distance| Speed) = Speed σ 2 . Compare the estimates and their standard errors with the un weighted case. Based on the un-weighted model, use a...

Refit the quadratic regression model assuming Var(Distance| Speed) = Speed σ₂. Compare the estimates and their standard errors with the un weighted case.

Based on the un-weighted model, use a sandwich estimator of variance to correct for non-constant variance. Compare with the results of the last sub problem.

Fit the un-weighted quadratic model, but use a case resampling bootstrap to estimate standard errors, and compare with the previous methods.