Does the knee surgery work, or just the belief in it?
Patients who undergo a popular knee operation report less pain afterward, and surgeons take this as proof the procedure works. A research team proposes a startling control: some volunteers get a "sham" surgery, an anesthetic and a small incision but none of the actual repair.
Why would a serious trial include a fake surgery, and what does the comparison isolate?
Your answer
This one is open-ended. Work it through, then check your reasoning against the full solution.