Experiments

• Evaluating Lab Experiments 


  • + High control over extraneous variables
  • - High control lowers ecological validity due to artificiality of research
  • + High control means procedures are generally replicable
• Evaluating Field Experiments


  • + Natural settings means high ecological validity and realism
  • - Low control over extraneous variables lowers internal validity
  • - Ethical issues if participants aren't aware they're in a study
• Quasi Experiments 


  • Contains a naturally occurring IV which already exists
  • A difference between people such as gender, age or a personality
• Evaluating Quasi Experiments 


  • - Participants can't be randomly allocated to research conditions
  • - No control over extraneous variables - makes it difficult to be sure factors e.g, age, gender, ethnicity have affected the DV
• What is the purpose of experiments in psych?


  • Experiments attempt to establish cause and effect between an IV and DV
  • IV = what is manipulated
  • DV = what is measured
  • Extraneous variables = what could affect the DV - need controlling
  • Uncontrolled extraneous variables become confounding variables
• Natural Experiments


  • Researchers don't manipulate the IV
  • They examine the effect of an existing IV on the DV
  • IV is naturally occurring (e.g a flood or earthquake)
• Lab Experiments


  • Researcher manipulates the IV and measures the DV under controlled conditions to prevent confounding variables
  • Participants usually know they're partaking in a study
• Field Experiment

  • Researcher manipulates the IV and measures DV in natural conditions
  • " Field" = anywhere which isn't a lab
  • Participants may not know they're in a study
• Evaluating Natural Experiments

  • + Naturally occurring IV means high levels of external validity
  • - Naturally occurring IVs mean things that can be studied that would otherwise be unethical to research