Types of experiment

• what is laboratory experiment?

  experiment that takes place in a highly controlled environment whereby not always in a lab as long as conditions are controlled
• what are field experiments ?

  An experiment where the IV has been manipulated in a natural , more everyday environment , not in a lab but variables still being well controlled
• what are quasi experiments?

  an experiment where the IV is based on naturally existing differences between people ; IV cannot be changed and DV may be naturally occurring e.g age , gender
• what are natural experiments?

  experiments whereby the researcher has no control over the IV = cannot change it as something or someone else causes the IV to vary e.g before and after an earthquake
• can pps still be tested in a lab in a natural experiment ?

  yes as it is only the IV that is natural
• what is a strength for laboratory+ quasi experiments?

  P - high internal validity

  E - high degree of control over confounding and extraneous variables

  E - researcher can ensure effect on DV is due to the manipulation of IV

  L - can be more certain about demonstrating a cause and effect relationship in the study
• what is possible since lab experiments are highly controlled?

  can be easily replicable as it is highly controlled = no new extraneous variables introduced when replicated (vital to check if a results of a study are valid)
• Limitation: lab experiment

  P - lack generalisability

  E - lab environ may be artificial = not like everyday life

  E - unfamiliar context pps may behave in unusual ways so cannot be generalised beyond research setting = low external validity + pps aware theyre being tested (as they are in a lab setting) so may respond to demand characteristics

  L - high degree of control makes experiment lack generalisability and low external validity
• Strength: field experiments

  P - high external validity

  E - higher mundane realism as environment is more natural

  E - = results / behaviour is more natural and authentic unlike lab ex as pps more likely to be unaware they are being studied = less likely for demand characteristics to be present

  L - manipulated IV removes possible extraneous variables e.g DC
• Limitation: field experiments

  P - ethics may be questioned

  E - natural environment = pps may be unaware they are being studied

  E = pps cannot give consent to being studies so such research might constitute an invasion of privacy

  L - important ethical issues which may affect the morality of study
• limitation: field experiments

  P - validity can be questioned

  E - increased mundane realism due to natural setting = loss of control over EVs + CVs

  E = cause and effect between IV and DV may be harder to establish and precise replication is often not possible

  L - the lack of replicability = harder for study to me verified / reduces validity of study
• Strength: Natural experiements

  P - high external validity

  E - involves the study of real-world issues and probs

  E - e.g before and after of a natural disaster and the effects it has on stress levels

  L - can be generalised to different everyday issues
• Limitations: Natural experiments

  P - lack of generalisability

  E - natural occurring events are rare and different

  E - cannot generalise or replicate = reduces validity of natural studies

  L - not applicable to numerous situations
• Limitations: Natural experiments+ Quasi experiments

  P - low internal validity

  E - lack of control over CVs and EVs as pps cannot be randomly allocated to experimental conditions

  E - e.g study of Romanian orphans IV was whether they were adopted early or late (many differences e.g late adoptions may have been less sociable = less appealing for prospective parents)

  L - harder for researcher to be certain whether the DV was affected by the IV