Research issues

• Extraneous variable

  Any variable, other than the IV, that may affect the DV if it is not controlled. EVs are essentially nuisance variables that do not vary systematically with the Iv.
• Confounding variables

  A kind of EV but the key feature is that a confounding variable varies systematically with the IV. Therefore we can't tell if any change in the DV is due to the IV or the confounding variable.
• Demand characteristics

  • Any cue from the researcher or from the research situation that may be interpreted by the ppts as revealing the purpose of an investigation. This may lead to a ppt changing their behaviour (please-u effect and screw-u effect).
  • If the ppts figure out what the experiment is their behaviour is no longer natural- an Ev that may affect the DV.
• Investigator effects

  • Any effect of the investigator's behaviour (conscious or unconscious) on the research outcome (the DV). This may include everything from the design of the study to the selection of, and interaction with theppts during the research process.
• Randomisation

  • The use of chance methods to control for the effects of bias when designing materials and deciding the order of experimental conditions.
  • Minimise effect of extraneous/ confounding variables.
  • Reduce researcher's unconscious biases when designing an experiment.
• Standardisation

  • Using exactly the same formalised procedures and instructions for all ppts in a research study.
  • All ppts should be subject to the same environment, information and experince.
  • Standardised instructions read to each ppt.
  • Such standardisation means that non-standardised changes in procedure do not act as EVs.
• Random allocation

  • An attempt to control for ppt variables in an independent groups design which ensures that each ppt has the same chance of being in one condition as any other.
  • Evenly distibute ppt characteristics across the conditions.
  • Random techniques- eg. pieces of paper with A or B written on them are placed in a hat and the researcher selects them one at a time to assign ppts to groups.
• Counterbalancing

  • An attempt to control for the effects of order in a repeated measures design: half the ppts experience the conditions in one order and the others in the opposite order.
  • Doesn't remove or prevent the problem, but attempts to balance out the effects.