Patients with pleural infections (fluid buildup in the chest) were randomly assigned to either placebo (n = 55), the treatment "tPA" (tissue plasminogen activator) (n = 52), the treatment "DNase" (deoxyribonucle-ase) (n = 51), or a combination of tPA and DNase (n = 52) in a double-blind clinical trial. Doctors used chest radiography to measure the percentage change, over 7 days, in the area of pleural fluid. The accompanying table shows the mean for each treatment group.24 The Yes/Yes cell is for the patients who received both tPA and DNase; the No/No cell is for the placebo patients.

For these data, SS(DNase) = 1226, SS(tPA) = 2836, SS(interaction) = 2870, and SS(within) = 91827.
(a) Construct the ANOVA table.
(b) Carry out an F test for interactions; us α = 0.10.
(c) Given the result of the test in part (b), is it appropriate to test the null hypothesis that tPA has no effect on change in area of pleural fluid? If so, then conduct that test using a = 0.05. If not, then explain why not.

Transcribed Image Text:

DNase? Yes No tPA? Yes No 29.5-17.2 -14.7 17.2