Final answer:
A double-blind experiment is used to control for experimenter and participant expectations, not to increase the placebo effect. It helps prevent bias in the experiment by keeping both researchers and participants unaware of group assignments.
Step-by-step explanation:
A double-blind experiment is not used to increase the placebo effect, but rather to control for experimenter and participant expectations. The placebo effect occurs when people's expectations or beliefs influence their experience. In a double-blind study, both the researchers and participants are unaware of which group they are in, helping to prevent bias in the experiment. This type of experiment is commonly used in clinical trials of vaccines, therapeutic drugs, and other medical treatments.