Note: * Precertification of denosumab (Prolia and Xgeva) is required of all Aetna participating providers and members in applicable plan designs. For precertification of denosumab (Prolia and Xgeva), call (866) 503-0857, or fax (866) 267-3277.
Observer Expectancy Effect. The observer expectancy effect, also called the experimenter expectancy effect, is a phenomenon that can occur when a researcherâs beliefs or expectations cause him or her to unconsciously influence the participants of an experiment. In order to conserve the internal validity of an experiment, researchers can use a double-blind experimental design.
EFFECT. 1  Something brought about by a cause or agent; a result. 2  The power to produce an outcome or achieve a result; influence: The drug had an immediate effect on the pain. The government's action had no effect on the trade imbalance. 3  A scientific law, hypothesis, or phenomenon: the photovoltaic effect.