Types of Experiments

• internal validity

  extent to which the researcher is measuring what they intented to - ensuring changes in DV are solely due to IV
• external validity


  extent to which findings can be generalised:

  - ecological

  - population

  - temporal
• ecological validity

  extent to which findings can be generalised to other settings/situations
• population validity

  extent to which findings can be generalised to other groups of people
• temporal validity

  extent to which findings can be generalised over time
• lab experiment


  carried out in highly controlled environments where researcher changes the IV
• field experiment

  IV is manipulated in natural/everyday settings
• quasi experiment

  IV is based on an existing difference between people e.g. age/gender
• natural experiment

  takes advantage of a pre-existing IV - variable would have changed whether experiment took place or not e.g. an event (romanian orphan studies)
• 2 + of lab experiments

  - high internal validity

  - reliable (repeatability)
• 3 - of lab experiments

  - low ecological validity

  - demand characteristics

  - low mundane realism
• 1 + of field experiment

  - high mundane realism/external validity
• 3 - of field experiments

  - lower internal validity

  - not reliable (can't easily repeat)

  - ethical concerns (should researcher carry out research)
• 2 + of natural experiments

  - provides opportunities for research that may not otherwise be undertaken

  - high external validity
• 3 - of natural experiments

  - limited opportunities for research

  - may be difficult to generalise findings

  - cofounding variables
• 1 + of quasi experiments

  - high internal validity/reliable
• 1 - of quasi experiments


  - may be co-founding variables (can't randomly allocate Ps)