A group of medical researchers investigated the effects of a drug called Pressure Drop X on lowering blood pressure in a group of women between the ages of 60 and 80 years old. The researchers did the following experiment and obtained the indicated results: One group of 150 women took a tablet containing Pressure Drop X for 3 weeks - 95 of these women experienced decreased blood pressure by at least 10%. Another group of 150 women were given a tablet with no added Pressure Drop X for 3 weeks - 10 of these women decreased their blood pressure by 10%. What are the controlled variables in this experiment?