Expectation bias (EB) occurs when an individual's expectations about outcome influence perceptions of one's own or others' behavior. In clinical trials, both raters and subjects may enter trials with expectations. Rater EB occurs when raters expect that subjects will improve over the course of the trial.

Some other examples:

• A person who believes that the stock market is going to crash may interpret any news about the stock market, even if it is neutral, as evidence that a crash is imminent.


• If someone believes that a certain politician is corrupt may interpret any information about that politician, even if it is neutral, as evidence of corruption.


• If someone thinks that a certain product is of high quality may interpret any information about that product, even if it is negative, as evidence that it is of high quality.

“Baldness Cure” lab researcher is throwing away results that don’t agree with what he expects is truth.