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Extraneous Variables are anything in a psychology experiment other than the independent  and dependent variables . The variables can present challenges and introduce errors, so it is important for experiments to control these extraneous factors. By holding the extraneous variables constant across all conditions of the experiment

For example, To help reduce test anxiety imagine that a researcher has devised an experiment to investigate whether giving study extra study time . The amount of study time the students have is the independent variable since it is what the experimenter manipulates and the amount of test anxiety the students experience is the dependent variable since it is what the researchers are measuring.

Extraneous variables such as the temperature of the room and the time of day the student is tested might have an influence on the independent variable as well. In order to control for these extraneous variables, the research should ensure that all students are tested at the same time of day in rooms of the same temperature.

There are two key methods that social scientists utilize to control for extraneous variables:Standardized procedures involve making all aspects of an experiment identical with the exceptions of the independent variable. As much as possible, researchers will recruit participants the same way, conduct the experiments in the same setting, and offer the same rewards for participation in the study. They will also give participants the same explanations and give similar feedback once the experiment is over. Other standardized procedures might involve performing the experiment at the same time of day for each condition and making the sure the conditions in the lab are the same for participants in all conditions same temperature, brightness, and noise levels.Random assignment means that all participants have an equal chance of being assigned to any of the experimental conditions. Using random assignment in an experiment helps reduce the likelihood that the personal characteristics of the participants themselves will have an influence over the independent variables. For example, in our previous example looking at study time and test anxiety, the researcher would use random assignment to assign students to either the experimental condition or the control condition. This reduces the likelihood that students who are simply less anxious in general will be assigned to one group while more anxious students are assigned to another group. Randomizing the assignment process ensures that all students have an equal chance of being assigned to either group.