experimental methods

• laboratory experiment 


  highly controlled environments

  participants are aware although they may not know the true aims of the study
• laboratory experiment - independent variables 


  controlled artificial settings --> ensure only thing manipulated is the IV and nothing alters the DV

  standardised procedures --> every participant gets the same experiment and experience
• laboratory experiment - strengths 


  high control over extraneous variables --> researcher can ensure that effect on DV is likely to be the result of manipulation of the IV

  replication --> other researchers can repeat the experiment to check results
• laboratory experiment - limitations 


  lack of mundane realism in the task --> less likely to have internal validity = not measuring what you intend to measure as there are participant effects in doing the task

  artificial setting --> lack of generalisability in the findings to other real life settings = low ecological validity
• field experiment 


  takes place in a natural setting within which the researcher manipulates the IV and records the effect in the DV

  can be conducted in hospital, classroom or street
• field experiment - independent variable 


  IV is still manipulated but conducted in a natural setting
• field experiment - strengths 


  high mundane realism of the task = high internal validity

  no demand characteristics --> natural behaviour

  high ecological validity = environment is more natural
• field experiment - limitations 


  less control = more difficult to control extraneous variables so harder to see cause of behaviour

  ethics = no informed consent

  replication = conditions are never exactly the same again so difficult to repeat the experiment to check results
• natural experiment 


  change in the IV is not brought about by the researcher but would have happened even if the researcher wasn't there.

  researcher records the effect on the DV they have decided on.
• natural experiment - independent variable

  IV is not manipulated by the researcher - it is an already existing IV

  researcher takes advantage of pre-existing IV

  IV is a change or event that is naturally occurring

  DV is measured usually in a natural setting
• natural experiment - strengths

  provides opportunities for researchers that may otherwise be undertaken for practical or ethical reasons

  high external validity - real life issues
• natural experiment - limitations 


  naturally occurring events happen very rarely = reduces opportunities

  limits scope for generalising findings to other similar situations
• quasi experiment

  examples =

  female vs male

  married vs non-married
• quasi experiment - independent variable 


  IV based on an existing difference between people

  no one has manipulated the variable is simply exists
• quasi experiment - strengths 


  carried out under controlled conditions and therefore share the strengths of a lab experiment
• quasi experiment - limitations 


  can't randomly allocate participants to conditions and therefore there may be confounding variables