In Chapter 3, a data set was presented that related math and reading scores to % minority and % poverty in 22 third-, fourth-, and fifth- grade classes.
a. Fit a model that relates math scores to reading scores, % minority, and % poverty. Include two indicator variables that will allow separate slopes and intercepts for the three grade levels.
b. Test at the .05 level whether the slopes were different for the three grade levels. Interpret your results.
c. Test at the .05 level whether the intercepts were different for the three grade levels. Interpret your results.
d. Do the conditions of normality and equal variances appear to be valid for your fitted model?
e. Note that the schools had an unequal number of students in each of the three grade levels. What is the impact on your fitted regression of ignoring the size of the school?