Extraneous and Confounding Variables

• Extraneous Variable - Unwanted extra variables other than the IV (1) that could have an effect on the DV, this would lower the internal validity of the study (1)
• Confounding Variables - When an extraneous variable is not controlled for and does affect the DV and so it becomes a confounding variable
• 3 main causes of extraneous variables:

  1. Situational factors - things to do with the environment the research is carried out in, e.g. task difficulty
  2. Participant variables - things to do with the participant, e.g. age (can only be used for IG design)
  3. Experimenter variables - things to do with the researcher, e.g. investigator effects