What are some methods of control in experiments?

Elimination: Removal of the extraneous variable (e.g. noise)

Constancy: Keeping the extraneous variable constant between two or more conditions (e.g. equal levels of noise)

Counter-balancing: Controlling variables that vary over time (e.g. practice or fatigue) by altering the conditions so that the variables have an equal effect on both conditions

Randomisation: Extraneous variables are varied unpredictably (e.g. random number generator)

Single-blind: Range of techniques used to prevent the demand characterstics influencing the results. Participant is not told which condition (control or experimental) they are placed in

Double-blind: Experimenter is kept in ignorance until after the data has been collected so that his/her bias’ and expectations don’t influence the results.