Research issues

• What are extraneous variables?

  • Any other variables that may potentially interfere with the independent variable.
  • They should be controlled or removed.
  • Where possible, researchers should Identify them at the start of the study and then take steps to minimise their influence.
  • They make it harder to detect a result.
• What are confounding variables?

  They change systematically with the independent variable, so we can’t be sure if any observed change in the dependent variable is due to the confounding variable or the independent variable.
• Demand characteristics

  • They are certain clues that may help them interpret what is going on.
  • Participants may act in a way that they think is expected and over-perform to please the experimenter, or deliberately under-perform to sabotage the results of the study.
  • Participants behaviour is no longer natural which is an extraneous variable that may affect the dependent variable.
• Investigator effects

  • The investigator‘s behaviour having an effect on the dependent variable.
  • Can refer to any action of the researcher that is related to the study’s design such as the selection of participants, the materials, and the instructions.
• Randomisation

  • Used to minimise the effect of extraneous / confounding variables.
  • Refers to the use of chance methods to reduce the researchers unconscious biases when designing an investigation.
• Standardisation

  • Using exactly the same procedures and instructions for all participants in a study.
  • E.g. same environment, information, and experience.