evs and controlling them

• what are extraneous variables?

  Variables that are not of interest in a study but can potentially influence the outcome
• what are confounding variables?

  Factors that can influence the relationship between the independent and dependent variables.
• what are demand characteristics?


  Cues in an experiment that participants use to determine the aim of the study and can change ppt behaviour
• what are investigator effects?

  any effect of investigators behaviour on outcome of research
• randomisation?

  use of chance when designing investigations to control effects of bias
• standardisation?

  using exact same standardised prodecdures for all ppts in research study to prevent evs
• controlling situational variables = same environment for everyone taking part with standardised conditions
• controlling ppt variables = repeated measures
• investigator effects being controlled by standardised instructions and being trained in same way
• order effects controlled by counterbalancing
• social desirability reduced by doing experiment alone and taking away peer pressure
• how to control placebo effect = perform double blind trials
• controlling demand characteristics using single blind design
• investigator effects controlled by double blind design