Extraneous and confounding variables

• extraneous variable - any variable that could affect the results that does not vary with the independent variable
• confounding variable - a variable that varies with the independent variable and affects the results
• order effects - when participants complete multiple conditions and so their performance could be affected by them having the chance to become bored or fatigued or to gain practice
• participant variables - when participants performance could be affected by their individual differences
• investigator effects - when participants results could be affected by the characteristics and/or the behaviour of the investigator
• situational variables - when participants performance could be affected by the differences in situation
• task variables - when participants performances could be affected by differences in the nature or difficulty of the task they are completing