Experimental Methods

• Laboratory experiment

  experiments conducted under controlled conditions where the researcher will try to control as many extraneous variables as possible and use standardised procedures
• In a lab experiment, the researcher manipulated the IV to see the effect of this on the DV
• In a lab experiment, participants usually know they're in an experiment although they may not know the true aims
• Field experiment

  these experiments are carried out in an ordinary setting (outside of a lab) in which the researcher manipulates the IV to see the effect of this on the DV
• In a field experiment, participants may not always know they're taking part in an experiment
• Natural experiment

  the researcher does not directly manipulate the IV, as it occurs naturally i.e. it would've changed even if the researcher had not been there. The research is measuring the effect of something that is already happening
• A natural experiment is carried out when it would not be possible to for ethical or practical reasons to deliberately manipulate the IV
• Quasi-experiment

  contain a naturally occurring IV, which is a difference between people that already exists (i.e. gender, age), so participants cannot be randomly allocated to conditions. It is similar to a lab experiment
• In a quasi-experiment, the researcher examines the effect of the naturally-occurring IV on the DV, but the IV has not been made to vary
• Strengths of a lab experiment:

  • high control over variables which increases internal validity - this can conclude cause and effect
  • can be easily replicated to check that the same results occur again - this helps to ensure that the results are more reliable