Experimental methods

• Quasi experiment 


  Can't use random allocation as they are the condition. Impossible for researcher to directly manipulate the IV as the IV is usually stuff like gender or existence of a mental disorder. The IV is dispostional as its a characteristic of the individual.

  +use of controlled lab conditions so standardised.

  +ecological validilty: research is less artificial than lab settings, can generalise the results to real life.

  -PP allocation: you can't randomly allocate pp into each condition so can be affected by confounding variables.
• Natural experiment 


  The IV isn't manipulated as it's a naturally occurring event. The researcher has little control over the social conditions of the experiment.

  +lower demand characteristics: PP might not know they are in a study so behaviour is normal and isn't changed.

  +ethical: it's possible to investigate areas that would be impossible to manipulate under lab conditions.

  -causal relationship: researcher doesn't manipulate IV.

  -Likelihood of situation happening again: may be a rarely occurring situation, reduces chances of replication.
• Field experiment 


  Take place in an environment where behaviour would naturally occur. e.g. casino to study how long gamblers stay on a slot machine.

  IV (key variable) is manipulated by researcher in an attempt to control extraneous variables that may influence the DV.

  +high ecological validity: no lab setting so can be generalised to real life

  +lower demand characteristics: PP are unaware they are in a study.

  -replication: procedures are not standardised so difficult for replication

  -Ethical issues: there is a lack of informed consent as don't know they are a part if the experiment.
• Lab experiment 


  highly controlled and standrdused envirnment where ut's easy to control and manipulate variables. IV is manipulated by the researcher and it's effect on the DV is measured.

  +high control: extraneous variables can easily be controlled and replication can happen so can asses findings for reliability.

  +causal relationship: control of extraneous variables which are not the IV so may influence the DV.

  -demand charcteristics: PP know they are in a study and may change behaviour so not true behaviour is shown.

  -low ecological validity: lab settings so no real life behaviour.