The objective of a study by Romita et al. (A-9) was to determine whether there is a different response to different calcium channel blockers. Two hundred and fifty patients with mild-to moderate hypertension were randomly assigned to 4 weeks of treatment with once-daily doses of(1)lercanidipine,(2)felodipine,or(3)nifedipine.

Prior to treatment and at the end of 4 weeks,each of the subjects had his or her systolic blood pressure measured. Researchers then calculated the changeinsystolicbloodpressure.Whatisthetreatmentvariableinthisstudy?The response variable? What extraneous variables can you think of whose effects would be included in the error term? What are the "values" of the treatment variable? Construct an analysis of variance table in which you specify for this study the sources of variation and the degrees of freedom.