Extraneous and Confounding Variables

• What is an extraneous variable?

  An extraneous variable is a variable that does not vary systematically with the independent variable but may affect the dependent variable.
• Why are extraneous variables problematic in experiments?


  They make it difficult to detect cause and effect between the independent and dependent variables.
• What is a confounding variable?

  A confounding variable is a variable that is not the independent variable but varies systematically with it.
• How can confounding variables affect the results of a study?

  Changes in the dependent variable may be due to the confounding variable rather than the independent variable, making the outcome meaningless.
• What are the four types of extraneous variables?

  The four types are situational variables, participant/person variables, experimenter/investigator effects, and demand characteristics.
• What are situational variables and why should they be controlled?

  • Situational variables are aspects of the environment that might affect participant behavior (e.g., noise, temperature, lighting).
  • They should be controlled to ensure they are the same for all participants.
• What are participant/person variables?

  • Participant/person variables refer to individual differences among participants that could affect results (e.g., mood, intelligence, anxiety).
• What are experimenter/investigator effects?

  • Experimenter effects occur when the experimenter unconsciously conveys to participants how they should behave, leading to experimenter bias.
• What are demand characteristics in an experiment?


  • Demand characteristics are clues in an experiment that convey to participants the purpose of the research.
• What are demand characteristics in research studies?


  They are cues that enable participants to guess the purpose of the study.
• How might participants respond to demand characteristics?

  Participants may try to please the researcher or annoy them by giving expected or unexpected results.
• What is the 'screw you effect' in research?

  It is when participants guess the purpose of the research and intentionally give wrong results.
• What are some reasons participants might act unnaturally in a study?

  Participants may act unnaturally due to nervousness, fear of evaluation, or social desirability bias.
• What are investigator effects in research?

  They are ways in which researchers unconsciously influence the results of their studies.
• How can physical characteristics of investigators influence research results?

  Physical characteristics like age or ethnicity may affect how participants respond.
• What are less obvious personal characteristics of investigators that can influence results?

  Characteristics such as accent or tone can influence how participants respond.
• How might investigators be biased in their interpretation of data?

  Investigators may unconsciously find what they expect to find in the data.
• What are the ways of dealing with extraneous variables in research?

  • Single blind design: Participants are unaware of the research aims or conditions.
  • Double blind design: Both participants and researchers are unaware of the aims/hypothesis.
  • Experimental realism: Engaging tasks to focus participants on the task rather than observation.
• What is a single blind design in research?

  It is a design where the participant is not aware of the research aims or which condition they are receiving.
• What is a double blind design in research?

  It is a design where both the participant and the researcher are blind to the aim or hypothesis of the study.
• What is experimental realism in research?

  It refers to making the task engaging so that participants focus on the task rather than being observed.
• How can standardization help overcome investigator effects?

  • Standardized instructions ensure consistency.
  • Instructions must be in a verbatim format for clarity.
  • Include a check to confirm participants understand their tasks.