Types of Experiment

• Internal validity


  Whether the effects observed in a study are due to the manipulation of the IV and not some other factor
• External validity


  Extent that research can be generalised beyond the results to other people
• Mundane realism


  The degree to which the materials and procedures involved are similar to events that occurred in the real world
• cause-and-effect relationship


  Relationship in which one event (the cause) makes another event happen (the effect).
• Laboratory experiments

  -occurs in a controlled environment

  -researcher can manipulate the IV and measure the DV

  -can control EVs
• Evaluation of Laboratory Experiments

  STRENGTHS

  -high control over EVs and CVs, high internal validity

  -easy to replicate

  WEAKNESSES

  -lacks generalisability

  -lacks mundane realism

  -participants are aware they're being tested
• field experiment


  • occurs in natural setting
  • IV can be manipulated, DV measured
• Evaluation of field experiments

  STRENGTHS

  • high mundane realism
  • participants are unaware that they are being studied

  WEAKNESSES

  • can't control EVs or CVs
  • Ethical issues: consent
• Natural experiments


  • no control over IV
  • IV would have occurred even if researcher wasn't studying it
  • IV is natural
• Evaluation of natural experiments

  STRENGTHS

  -opportunities for research that may not be conducted otherwise

  -high external validity

  WEAKNESSES

  -rare

  -impossible to randomly allocate participants to different conditions
• Quasi experiments


  -IV is based on pre-existing differences

  -IV can't be manipulated
• Evaluation of quasi experiments

  STRENGTHS

  -controlled experiments, high internal validity

  -easy to replicate

  WEAKNESSES

  -CVs can be an issue

  -participants can't be randomly allocated to different conditions