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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.
Experimenter bias occurs when the measurements obtained in a study are influenced by the experimenter's expectations regarding the outcome of the study. A researcher knows the predicted outcome of a research study and is in a position to influence the results,either intentionally or unintentionally.