In a study to compare the absorption rates of three drugs, A, B, and C, a predetermined dose of each was administered to six subjects (18 subjects in all). Three subjects within each group were given the drug orally; the other three received it intravenously. For each test subject, the amount of drug absorbed into the blood within four hours of its administration was measured.

Each subject's body weight and age were also measured, in case these variables also influence drug absorption. The response variable in this study was Y=the amount of drug absorbed within four hours of its administration. The conditions under which the measurements are made could be determined by the type of drug administered (A, B, or C), the method of administering the drug (intravenous or oral), the subject's body weight, and the subject's age. All other variables--such as gender and blood pressure--were considered unimportant as indicators of the rate of drug absorption.

Suppose the investigators wanted to use the observed responses to see: (1) if the absorption rate of any one of the three drugs depended on the way it was administered; and (2) if there were any differences between the absorption rates of the three drugs in either of the two modes of application.

a. Argue that this is an experimental study and identify the experimental factors.

b. What are the treatments and experimental units?

c. How many replications are there for each treatment?

d. Are there any confounding variables? describe