Control of variables

• Extraneous variables

  Any variable other than the IV that may have an effect on the DV

  Participant or situational
• Demand characteristics

  Any cue from the researcher or from the research situation that may reveal the true aims of the investigation - the participant may change their behaviour within the research situation
• 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.

  These are a type of extraneous variable
• Investigator effects

  Any effect of the investigator's behaviour (conscious or unconscious) on the research outcome
• Randomisation

  The use of chance in order to control for the effects of bias when designing materials and deciding the order of conditions
• Standardisation- dealing with situational variables

  Using exactly the same procedures and instructions for all participants in a research study where possible
• How do we deal with demand characteristics?

  Single blind technique - the participants are unaware of the specific aims and hypotheses and which condition they are in
• How do we deal with investigator effects?

  Double blind technique - neither the participant nor the researcher are aware of the aims and hypotheses