experimental methods

• laboratory experiments


  aim to establish a cause and effect relationship between IV (manipulated by researcher) and DV (measured) - conducted in a controlled environment using standardised procedures
• Laboratory advantages

  high degree of control over variables - controlled setting, extraneous variables can be controlled - lighting and temperature can be controlled - high internal validity

  easy to replicate - can be easily repeated in a lab - e.g. lighting and temperature can be the same - easily tested for reliability
• Laboratory disadvantages


  high demand characteristics - participants aware they're taking part, may change behaviour - participants may behave differently to please the researcher - low internal validity

  low ecological validity - artificial setting, doesn't reflect behaviour in real world - may behave differently at home or at work - can't be generalised to real life settings
• field experiments

  establish cause and effect relationship between IV and DV - conducted outside laboratory in real life environment or situation - might take place in school or on the street
• field experiment advantages


  high ecological validity - real life setting so should reflect natural behaviour - participants studied in setting where behaviour being measured naturally occurs - findings can be generalised to other real life settings

  low demand characteristics - participants usually unaware they're taking part in research - participants won't be able to work out aim and start behaving differently
• field experiment disadvantages


  low degree of control over variables - outside controlled setting, difficult to control extraneous variables - lighting and noise levels can't be standardised - low internal validity

  difficult to replicate - conditions used for one study difficult to repeat in another - temperature and noise levels may vary each time its replicated - can't be easily tested for reliability
• natural experiments 


  aim to establish cause and effect relationship between IV and DV - IV varies naturally and isn't deliberately manipulated by researcher - take advantage of natural events
• natural experiment advantages 


  high ecological validity - usually takes place in real life setting so should reflect natural behaviour - participants in setting where behaviour being measured usually occurs - findings can be generalised to other real life settings

  provides opportunity for research that may not otherwise take place - allows researchers to study situations where its not possible to manipulate variables - e.g. unethical to manipulate variables (age child is adopted) - increased knowledge and understanding
• natural experiment disadvantages 


  random allocation to conditions not possible - conditions occur naturally so may be biased - people in one condition may be more intelligent - low internal validity

  difficult to replicate - conditions used for one study very difficult to repeat - noise levels and lighting vary a lot each time repeated - findings can't be very easily tested for reliability
• Quasi experiment 


  aim to establish a cause and effect relationship between an IV and DV - IV doesn't vary at all because conditions already exist like the study of age or gender
• quasi experiment advantages


  high ecological validity - real life setting so should reflect natural behaviour - studied in setting where behaviour being measured usually occurs - findings can be generalised to other real life settings

  provides opportunity that may not otherwise take place - allows researchers to study situations where it isn't possible to manipulate variables - e.g. when studying gender or age - increase knowledge and understanding
• quasi experiment disadvantages 


  random allocation to conditions not possible - IV already exists which may be biased - one condition may be naturally more intelligent - low internal validity

  difficult to replicate - conditions used for one study will be difficult to repeat in real world - noise levels and temperature may vary each time its repeated - findings can't be easily tested for reliability