Experimental Design Math Example 4
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Example 4
hardWhat is a placebo, and why is blinding important? Describe the placebo effect quantitatively: if 30% of placebo patients improve, what must a drug achieve to demonstrate its own effect?
Solution
- 1 Placebo: an inert treatment (sugar pill) given to the control group to make groups psychologically equivalent
- 2 Placebo effect: patients improve simply because they believe they are being treated; this is a real psychological/physiological response
- 3 Blinding: prevents participants knowing their group (prevents placebo effect differences); double-blind prevents researcher bias in assessment
- 4 Drug threshold: if 30% improve on placebo, the drug must show significantly higher improvement (e.g., 50%+) to demonstrate efficacy beyond placebo alone
Answer
Placebo controls for the placebo effect (30% improvement). Drug must exceed 30% to show real efficacy.
The placebo effect is a real, measurable phenomenon in clinical trials, often causing 20-40% improvement for conditions like pain and depression. Without a placebo control, we cannot distinguish drug effects from psychological expectation effects.
About Experimental Design
The deliberate planning of a study in which the researcher imposes treatments on subjects and measures responses, using control groups, randomization, replication, and (where possible) blinding to establish cause-and-effect relationships.
Learn more about Experimental Design →More Experimental Design Examples
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