Experiment types

• What are the four types of experiment?

  • Lab
  • Field
  • Natural
  • Quasi
• What is a lab experiment?

  • Conducted in a highly controlled environment
  • Independent variable is manipulated
• What is a field experiment?

  • Conducted in a natural setting
  • Independent variable is manipulated
• What is a natural experiment?

  • Independent variable changes naturally
  • Dependent variable and setting may be natural or in a lab
• What is a quasi experiment?

  • Independent variable based on an existing difference between people e.g. age or gender
  • Effect on dependent variable recorded
• Evaluation of Lab experiments:

  +High internal validity (control over confounding and extraneous variables, cause and effect shown)

  +Replication more possible (support for findings)

  -Low external validity (generalisability, lacks realism)

  -Low internal validity (demand characteristics)
• Evaluation for Field experiments:

  +Higher external validity (more authentic / real)

  -Lower internal validity (less control)

  -Ethical issues (consent not possible)
• Evaluation of Natural experiments:

  +Only option for practical and ethical issues (e.g. Romanian orphan study)

  +High external validity (real world problems)

  -Limited opportunities

  -No random allocation

  -Low realism in a lab

  -No manipulation of independent variable (can't claim cause and effect)
• Evaluation of Quasi experiment:

  If in lab:

  +Same as lab

  -Same as lab

  -can't randomly allocate (confounding variables)