When Experiments Are Used to Determine Whether Therapy Is Effective

Multiple Choice

When experiments are used to determine whether therapy is effective, the therapy can be deemed effective only if the

A) control group shows improvement, but the experimental group shows none.
B) waiting list group shows dramatic improvement over the experimental and control groups.
C) experimental group shows more improvement than the control group.
D) experimental and waiting list groups show improvement and the control group shows no improvement.