Control of Variables

• What should happen to any variables that interfere with the IV or DV?


  They should be removed from the experiment or well controlled
• Define extraneous variables?


  Refers to any other variable which is not the IV that affects the DV and does not vary systematically with the IV
• Give an example of an extraneous variable?


  age of participants - this does not confound the results of the study but instead make them harder to detect
• Define confounding variables?


  A variable other than IV that has an effect on the DV, confounding variables do change systematically with the IV.
• What is difficult about confounding variables?


  It becomes difficult for the researcher to be sure of the origin of the impact of the DV as the confounding variable - not the IV could have been the cause
• Gice an example of a confounding variable?


  The time of day the experimental task is done- those who complete the memory test later in the day may be more tired so do worse which obscures the relationship between lack of sleep and memory performance
• What is meant by demand characteristics?

  Refers to any cue the researcher/ research situation might give which makes the participant feel like they can guess the aim of the investigation
• What can demand characteristics cause?


  Can cause the participant to act differently within the research situation from how they would usually act
• What is participant reactivity?


  When participants from the start of the experiment are trying to figure out what’s going on in the new situation they find themselves in- so change their behaviour to fit the situation other than acting naturally
• What is the please you effect?

  When the participant acts in a way they think the researcher wants them to
• What is the screw you effect?

  When participants intentionally underperform in the experiment to sabotage the study's results
• What consequences does the please you & screw you effect have?


  This affects the validity of the results hence demand characteristics providing a problem for research
• Define investigator effects?


  Refers to any unwanted influence from the researcher’s behaviour (conscious/unconscious)on the dependent variable measured (results of the study)
• What factors can cause investigator effects?


  • Design of the study
  • Selection of participants
  • Interaction with each participant during research investigation
• How are randomisation and standardisation used in an experiment?

  To minimise the effects of extraneous/confounding variables
• Define randomisation?

  The use of chance to reduce effectors of bias from investigator effects. Can be done for the design if materials/ deciding the order of conditions
• Define standardisation?

  Using the exact same formalised procedures and instructions for every single participant involved in the research process, allowing them to eliminate non standardised instructions as being possible extraneous variables