Practice Placebo Effect in Statistics

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

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Quick Recap

The placebo effect occurs when participants change their response because they believe they are receiving a treatment, even if the treatment itself has no active effect.

Expectations can change behavior and reported outcomes. That means a study can look successful even when the treatment itself is not the true cause.

Showing a random 20 of 50 problems.

Example 1

hard
Researchers find that more expensive-looking placebo pills produce stronger placebo effects than cheaper-looking ones. What does this say about the placebo mechanism?

Example 2

challenge
A trial gives the treatment group a pill with mild side effects and the placebo group an inert pill with none. Patients guess their group from side effects. Explain how this 'unblinding via side effects' can inflate the apparent treatment effect through the placebo mechanism.

Example 3

easy
An inert substance designed to look like real treatment is called a ____.

Example 4

medium
A homeopathic remedy is shown to outperform no-treatment but not outperform placebo. What's the appropriate conclusion?

Example 5

easy
In which kinds of studies is the placebo effect most relevant: human self-reported outcomes or weights of rocks?

Example 6

medium
Why is the placebo effect a particular problem for outcomes like pain or mood rather than blood test values?

Example 7

hard
Why might the placebo effect appear stronger in unblinded trials than blinded ones?

Example 8

easy
True or false: the placebo effect can occur even in objective measurements like blood pressure.

Example 9

medium
A pain study's treatment group improved 50% and placebo group improved 48%. What does the small gap suggest about the drug's true effect?

Example 10

easy
The placebo effect shows that a study can look successful even when what is true?

Example 11

easy
Two patients with chronic back pain are told one will get a new drug and the other a placebo — but both get the placebo. Who is more likely to feel some relief?

Example 12

medium
Could the placebo effect explain why some people swear by ineffective folk remedies?

Example 13

medium
The 'nocebo effect' is the negative twin of the placebo effect. What is it?

Example 14

challenge
A drug trial reports the treatment effect is significant at p=0.04p=0.04. The placebo effect (placebo − no-treatment) is much larger than the drug effect (drug − placebo). Critics call the trial 'practically pointless.' Explain their argument.

Example 15

easy
To detect the placebo effect, what should the control group receive?

Example 16

easy
Patients given a sugar pill they believe is medicine report feeling better. This change due to belief is called what?

Example 17

hard
Researchers analyze placebo response rates across 100 trials and find they have risen over recent decades. Give one plausible explanation.

Example 18

medium
A trial finds the treatment group improved 40% and the placebo group improved 25%. What portion is attributable to the placebo effect, and what to the drug's active effect?

Example 19

easy
Fill in the blank: The placebo effect is largest for outcomes that depend on _____ judgment.

Example 20

hard
A trial of a depression drug uses a placebo control. Both arms show large improvements over 8 weeks. What additional control would help distinguish placebo from natural improvement?
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