Final answer:
To test a new drug for treating depression, you would have a control group receiving a placebo and an experimental group receiving the drug. The independent variable is the drug treatment, and the dependent variable is the level of depression symptoms.
Step-by-step explanation:
To design an experiment to test a new drug to treat depression, you would need to have two groups. The control group would receive a placebo or an inactive substance, while the experimental group would receive the actual drug being tested.
The hypothesis would be that the new drug will have a positive effect on reducing depression symptoms. The independent variable (IV) would be the drug treatment, and the dependent variable (DV) would be the level of depression symptoms.
A potential confounding variable could be the participants' previous experience with other depression treatments. The operational definition of depression would involve measuring the severity of depressive symptoms using a validated depression rating scale.