Masking for Performance Bias

Masking or Blinding protects against Performance Bias

If study participants or study providers know who is in which group, it is possible that the study groups will receive different types of care, or be exposed to other factors, beyond the treatment that the researchers are trying to study.

For example:

Participants in the treatment group of a diet study stopped exercising because they thought the diet pill would be enough to help them lose weight, leading to performance bias.

Doctors gave extra nutritional advice to the participants in the control group of a diet study, because they worried that they wouldn’t lose weight, leading to performance bias.