A researcher has designed a study to test the effects of different types of individual psychotherapy on people's levels of depression. She has randomly assigned people to one of three groups: a cognitive-behavioral treatment group, a psychodynamic treatment group, or a no-treatment control group. She then measures people's level of depression after the treatment. Which of the following statements is TRUE?
A) The treatment group is the dependent variable; depression is the independent variable.
B) Depression is the dependent variable; the treatment group is the independent variable.
C) Depression is the dependent variable; cognitive-behavioral treatment is the independent variable.
D) Cognitive-behavioral treatment is the dependent variable; depression is the independent variable.