7.2.8 Variables & controls

Independent variable - The independent variable changes or is manipulated so the effect on the dependent variable can be measured.

Dependent variable - measured by the researcher.

Operationalisation - clearly defining variables in terms of how they can be measured.

Extraneous variables - any variable, other than IV, that may influence the DV if it is not controlled. EVs are more unpredictable nuisance variables. Where possible, these are identified at the beginning of an experiment to have their influence minimised. Do not vary systematically.

Cofounding variables - any variable, other than the IV, that may have affected the DV so we cannot be sure of the true source of changes to the DV. Vary systematically with the IV, e.g. personality.

Demand characteristics - any cue from the researcher or research situation that may be interpreted by participants as revealing the true purpose of the investigation- may lead to a participant changing their behaviour within the research situation.

Investigator effects - any effect of the investigator's behaviour on the research outcome (DV). This may include everything from the design of the study to the selection of, and interaction with participants during the research process.

Randomisation - use of chance to reduce the effects of extraneous/confounding variables when designing materials and deciding the order of conditions.

Standardisation - using the same formalised procedures and instructions for all participants in a research study.