types of experiments

• Laboratory experiments


  Experimenter has full control over what happens in the experiment, environmental factors and instructions are highly controlled, only one factor (independent variable) changes between conditions
• Laboratory experiments


  • High internal validity, highly replicable
  • May lack external validity, ecological validity, and mundane realism, can suffer from demand characteristics
• Field experiments


  Conducted in the real world, natural setting, not a lab
• Field experiments


  • Increased external validity and ecological validity, reduced demand characteristics
  • Lack of control over extraneous variables, reduced internal validity, cannot randomly assign participants
• Natural experiments


  Levels of independent variable have already happened naturally, researcher just measures change in dependent variable
• Natural experiments


  • Allow research in areas not possible otherwise, high external validity
  • Lack of control over extraneous variables, reduced internal validity, cannot be replicated
• Quasi-experiments


  Researcher cannot randomly assign participants to different levels of independent variable, groups already exist
• Quasi-experiments


  • Only way to study certain factors like gender, age, mental health conditions
  • Confounding variables that differ systematically between conditions