Control of variables

Control of variables

Extraneous variables

• The only thing that should influence the DV is the IV 
• Any other variables that might potentially interfere with the IV should be controlled/removed
• These additional unwanted variables are extraneous variables and where possible, are identified at the start of the study by the researcher, who then taskes steps to minimise their influence
• Many EV are straightforward to control such as the age of ppts, lighting in a lab etc
• They do not vary systematically with the IV
• They do not confound the findings of the study, they may just make it harder to detect a result

 Confounding variables

• These do change systematically with the IV
• Personality is a confouding variable
• Cannot establish cause and effect

Demand charcteristics

• Ppts are not passive within experiments and are likely to be spending much of their time trying to make sense of…