=+34. A pharmaceutical company wants to begin testing a drug designed to reduce blood pressure. The company wants to test the drug by measuring the blood pressures of two samples of people, those who take the drug for a prescribed period of time and those who do not take this drug (or any other medications during the test period). Because researchers know that several human characteristics (e.g., age, weight, diet, exercise) may have considerable effects on the experimental results, they want to run their experiment as