Experimental Methods

• Experimental method

  Manipulation of variables in an attempt to establish a cause-and-effect relationship. There are 4 types.
• Laboratory

  Controlled environments, whereby standardised procedures are used and participants are allocated to experimental groups

  • Reliable (can be replicated due to standardised procedure)
  • Internally valid (controls extraneous variables)
  • Low in external validity (environment and tasks are usually artificial)
• Field

  Manipulation of IV in real life settings, sometimes PPs don't know they're being studied

  • Externally valid (natural setting means PPs behaviour will be normal)
  • Low in internal validity (difficult to control extraneous variables in real life settings)
• Natural

  IV varies naturally; experimenter does not manipulate it but records effects of DV

  • Externally valid (behaviour is normal because of real life setting)
  • Low in internal validity (difficult to control extraneous variables)
• Quasi

  IV occurs naturally, e.g. gender/age/eye colour. Researcher cannot manipulate and cannot randomly allocate PPs to different conditions

  • Reliable (takes place in controlled settings and can be replicated)
  • Low in internal validity (would be extraneous variables as they can't randomly allocate PPs to conditions)