a study is planned to compare the blood pressure lowering effect of two medications (drug A and drug B) in patients with elevated systolic blood pressure (SBP). Drug A is a newly developed medication lowering the elevated SBP and drug B is a commonly prescribed medication for high SBP. 80 newly diagnosed patients with high SBP are recruited into the study with half of them randomly assigned to drug A and another half to drug B for three months. each participant's blood pressure will be monitored during the study, but the change in SBP (mmHg) will be recorded as the difference between SBP measured at the end of the study and SBP measured on entering the study.

a) what type of the study is this?

b) how many factors (variables) are involved in this study? what are they?

c) what are the measurement scales for these factors (variables)?