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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.
Generally, one or more variables are manipulated to determine their effect on a dependent variable. The experimental method. is a systematic and scientific approach to research in which the researcher manipulates one or more variables, and controls and measures any change in other variables. Experimental Research is often used where: 1  There is time priority in a causal relationship (cause precedes effect). 2  There is consistency in a causal relationship (a cause will always lead to the same effect). 3  The magnitude of the correlation is great.