This problem considers the (fictitious) study designed to compare two treatments for the relief of heartburn, described by the data set of Table 25.6. One of two treatments (A = active = 1, P = placebo = 0) has been randomly allocated to two groups of 15 subjects each, and each subject receives the same treatment for both meals. The outcome variable is a continuous measure of physical discomfort measured by a questionnaire administered to each subject two hours after receiving the treatment. Edited computer output from SAS's MIXED procedure is provided below.
a. Why is it appropriate to do a correlated data analysis here?
b. Why doesn't it matter what correlation structure is chosen (other than "independence") for carrying out a correlated data analysis of these data?
c. Specify the subject-specific scalar model form used in this analysis.
d. Specify the subject-specific matrix model form used in this analysis.
e. What do you conclude about whether or not there is a significant difference between the effects of the two treatments on the amount of discomfort experienced by study subjects? Explain briefly