any variable other than the independent variable (IV), that may have an effect on the dependent variable (DV) if it is not controlled. EV’s are considered to be nuisance variables.
Confounding variables
Any variable, other than the IV that may have affected the DV so we cannot be sure of the true source of the changes to the DV. Confounding variables may vary systematically with the IV.
Demand characteristics
Any cue from the researcher from the research situation that may be interpreted by the participants as revealing the purpose of the investigation.
Investigator effects
Any effect of the investigator’s behaviour (conscious or unconscious) on the research outcome (the DV).
Standardisation
Using exactly the same formalised procedures and instructions for all participants in a research study.
Randomisation
the use of chance in order to control for the effects of bias when designing materials and deciding the order of conditions.
types of extraneous variables
Gender: could be evenly spread between groups.
Age: just use A Level students.
Consumption of other energy drinks: monitor what participants drank a couple of hours before the experiment.
