Control of Variables

• Extraneous Variables

  An extraneous variable is any variable other than the independent variable which affects the dependent variable
• Cofounding Variables


  This is when an extraneous variable actually does affect the DV, so we cannot say if the IV or the cofounding variable(s) affected the study.

  E.g. Personality. In an experiment to see whether a formal or casual environment causing more social interactions, perhaps everyone in the casual could be extraverted, so we do not if setting or personality explains the outcomes of the study.
• Demand Characteristics


  These occur when the participants try to make sense of the research and act accordingly to support the aim of the research or go against it.
• Investigator effects


  Occurs when a researcher unintentionally, or unconsciously influences the outcome of any research they are conducting.
• Randomisation


  the act or process of ordering or selecting people, things, or places in a random way, as in a sample or experiment, especially in order to reduce bias and interference by irrelevant variables
• Standardisation


  keeping everything the same for all participants so that the investigation is fair.
• Counterbalancing


  Ensures that order effects (Practice/Boredom) are split evenly across conditions when you have participants taking part in more than one condition

  e.g. randomly Bob and Aimee will do condition A first, then B

  and Janet and Maisie will do condition B, then A
• Order Effects


  An order effect occurs when participants' responses in the various conditions are affected by the order of conditions to which they were exposed, for example practice or boredom