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Explain why a waitlist control is insufficient in this scenario. What does the osteoarthritis knee study reveal about how expectations and the placebo effect can influence physiological outcomes, and how does a sham surgery address this issue?
Case context: A research team wants to test the efficacy of a new surgical procedure for shoulder joint repair. They plan to compare a group of patients receiving the new surgery against a group that receives no treatment at all (a waitlist control). Based on the findings of the osteoarthritis knee study, a peer reviewer suggests that a waitlist control is insufficient to demonstrate the true efficacy of the surgery.
Question: Explain why a waitlist control is insufficient in this scenario. What does the osteoarthritis knee study reveal about how expectations and the placebo effect can influence physiological outcomes, and how does a sham surgery address this issue?
Sample answer: A waitlist control is insufficient because improvements in the treatment group could be caused by the placebo effect (the expectation of healing) rather than the physical surgery itself. The osteoarthritis knee study demonstrated that patients receiving sham surgery (only a tranquilizer and incisions) improved in knee pain and function just as much as those receiving the real surgery. A sham surgery control accounts for this by matching the expectations and sensory experiences of both groups, isolating the true physical efficacy of the operation.
Key points:
- Explains that a waitlist control fails to rule out expectation-driven improvements (placebo effects).
- References the osteoarthritis knee study where the sham surgery control group showed improvements equal to the treatment group.
- Explains that the placebo effect can cause physiological improvements in pain and function.
- Explains that sham surgery controls for expectation by keeping all aspects of the procedure (tranquilizer, incisions) identical except for the actual surgery.
Rubric: The response must explain that a waitlist control cannot rule out the placebo effect. It must reference the knee study to show that placebo/sham surgery can produce physiological improvements equal to actual surgery. Finally, it must explain that a sham surgery serves as a proper control by matching expectations and physical experiences (like incisions and anesthesia) across both groups.
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Research Methods in Psychology - 4th American Edition @ KPU
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In a study on osteoarthritis of the knee, participants who received a simulated surgical procedure—consisting of a tranquilizer and small incisions but no actual operation—showed improvements in knee pain and function that were equal to those of participants who received the real arthroscopic surgery.
In a study on knee osteoarthritis, a comparison group received a 'sham surgery' consisting only of a tranquilizer and small incisions without any actual procedure. This group demonstrated physiological improvements equal to those who received the real surgery. What is the most significant conclusion a researcher can draw from this finding?
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Explain why a waitlist control is insufficient in this scenario. What does the osteoarthritis knee study reveal about how expectations and the placebo effect can influence physiological outcomes, and how does a sham surgery address this issue?
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