experimental methods - types of experiment

• Types of Experiment

  • Laboratory experiment
  • Field experiment
  • Natural experiment
  • Quasi experiment
• What are lab experiments?

  An experiment conducted in a highly controlled environment where every variable can be carefully controlled. Researcher manipulates IV and records effect on DV
• What are field experiments?

  The IV is manipulated in a natural, everyday setting

  IV is still manipulated but experiment takes place in a natural setting
• What are natural experiments?

  The researcher takes advantage of a naturally occurring IV, therefore the researcher doesn't manipulate the IV
• What are quasi-experiments?

  Have an IV that is based on an existing difference between people (e.g. age or gender). No one has manipulated the variable, it simply exists
• What are the evaluation points to laboratory experiments?

  + well controlled

  + extraneous / confounding variables minimised (higher internal validity)

  + can be easily replicated

  
  

  - artificial situation so results lack generalisability (low external validity)

  - ppts know they are in an experiment (risk of demand characteristics)

  - tasks ppts carry out may not represent real life experience (low mundane realism)
• What are the evaluation points to field experiments?

  + less artificial in comparison to lab experiments is more natural - usually higher mundane realism and higher ecological validity

  + ppts usually unaware they are being studied

  
  

  - loss of control of extraneous variables

  - ethical issues (ppts unaware, consent, invasion of privacy)
• What are evaluation points to natural experiments?

  + allows research where IV can't be manipulated for ethical or practical reasons

  + enables psychologists to study real problems such as effects of a disaster on health (increased mundane realism and ecological validity)

  
  

  - naturally occurring event may only happen rarely, reducing opportunities for research and generalising findings to similar situations

  - can't demonstrate causal relationship because IV is not directly manipulated

  - random allocation of ppts to each condition not possible - confounding variables
• What are the evaluation points to quasi experiments?

  + allows comparisons between types of people

  + often carried out under controlled conditions so share strengths of lab experiments

  
  

  = can't randomly allocate ppts to conditions - confounding variables