Refer to Exercise 13.81.
a. Fit a second- order model relating math scores to reading scores, % minority, and % poverty with indicator variables for grade level. Does this model appear to provide a substantial improvement in fit over the first- order model?
b. Using your fitted model, estimate the average math score for a third- grade class having a reading score of 170, % minority of 40%, and % poverty of 30%. Provide both a point estimator and a 95% confidence interval.
c. Compare the estimators from the first- and second- order models.