Short Answer

A psychologist wants to design an experiment to test whether placing a copper coin on a bruise—a traditional folk remedy believed to speed up healing—functions as a placebo. How should the researcher design the control group's treatment to isolate the role of participant expectations from any active physical properties of the copper coin?

Question: A psychologist wants to design an experiment to test whether placing a copper coin on a bruise—a traditional folk remedy believed to speed up healing—functions as a placebo. How should the researcher design the control group's treatment to isolate the role of participant expectations from any active physical properties of the copper coin?

Sample answer: The researcher should design a control group that receives a sham treatment, such as a plastic coin painted to look exactly like copper, while keeping the participant's expectation of healing identical to the experimental group. By using a sham coin that lacks the active physical material (copper), the researcher can determine if any observed healing is due to the participant's expectation of improvement rather than the physical properties of the copper itself.

Key points:

  • The control group must receive a sham treatment (like a plastic coin) that looks like the folk remedy.
  • The control group treatment must lack the active physical/chemical property being tested (copper).
  • Both groups must have the same psychological expectation of improvement to isolate the placebo effect.

Rubric: The response must describe a control group receiving an inactive sham treatment (such as a lookalike plastic coin) that mimics the physical appearance of the folk remedy but lacks the hypothesized active physical properties (copper), while maintaining the same expectation of healing as the experimental group.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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