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.
Independent Variables. In experimental research, an investigator manipulates one variable and measures the effect of that manipulation on another variable. The variable that the researcher manipulates is called the independent, or grouping variable.