# AP Statistics : How to identify the placebo effect in an experiment

## Example Questions

### Example Question #1 : How To Identify The Placebo Effect In An Experiment

A study is trying to determine if a particular medication (Y) is effective in weight loss. Patients participating in the study were randomly assigned to groups A, B, C, D, or E. Group A will receive one dose of Y, Group B will receive two doses of Y, Group C will receive three doses of Y, Group D will receive four doses of Y, and Group E will serve as the control group.

Which group will be receiving the placebo (a sugar pill)?

Group A

Group C

Group B

Group E

Group D

Group E

Explanation:

The control group in an experiment typically receives placebo treatments (in this case - Group E). Since all of the other groups are receiving at least one dose of the medication, they are considered to be experimental groups.

### Example Question #1 : How To Identify The Placebo Effect In An Experiment

To test if vitamin C actually makes people feel better, a vitamin company decides to run a 5-day study where they give one group of 100 sick participants vitamin C pills and another group of 100 sick people placebo pills, and monitored another group of 100 sick people who took no pills.

At the end of the 5-day experiment, 90 participants in the vitamin C group reported feeling better. 30 participants in the no-pill group felt better after the 5-day period. Interestingly, 50 participants in the placebo group felt better after the 5-day period.

What could explain these numbers?

5 days is too long for the experiment.

5 days is too short for the experiment.

The placebo effect: some participants in the placebo group began to feel better because they thought they were taking something that would help them.

Vitamin C actually makes people feel sicker.

There is no logical explanation.