Refer to Exercise 16.1. After collecting the data and testing for parallelism of the four lines relating the reduction in blood pressure to the age of the subject, the researcher finds that there is significant evidence that the lines are not parallel.
a. Describe how would you test for differences in the adjusted treatment means?
b. Provide the form of the estimated mean response for supplement 1 for subjects of age 45 years.
c. The researcher wants to evaluate the supplements for subjects of age 80 years or older. What problems may she encounter using the data in her current study, if any?