Experimental research methods

• laboratory experiment (summary)


  • controlled environment
  • artificial setting which experimenter has set up and will control
  • variables can be carefully manipulated
  • participants are aware they are in a study, but may not know aims of the study
• laboratory experiments (strengths)

  +high internal validity - experimenter has control over research variables so it's certain any change in the DV is due to the IV

  + easy to replicate - due to high levels of control + standardised procedures, so results are same and can be tested + compared
• laboratory experiments (limitations)

  -low ecological validity - results cannot be generalised due to artificial setting, participants won't act normally

  -demand characteristics - know they are being tested so may change behaviour, reducing validity
• Field experiments (summary)

  • conducted in natural/ordinary environment
  • IV deliberately manipulated by researcher, who measures DV
  • participants unaware they are participating, so behaviour may be more natural (Pilivan 1969)
• Field experiments (strengths)

  + high ecological validity - results can be generalised, real life setting (mundane realism) so participants will act natural

  + lack of demand characteristics - as experiment is realistic, participants are unaware they are being studied so won't behave differently
• Field experiments (limitations)

  -low internal validity - experimenter has less control over variables so not certain that change in the DV is due to the IV

  -not easy to replicate - as there are less control variables, so it's hard for results to be tested and compared
• Natural experiments (summary)

  • conducted when it's not possible (ethical or practical reasons) to deliberately manipulate an IV
  • IV occurs naturally, not controlled by experimenter (Charlton et al, 2000)
• Natural experiments (strengths)

  +allows research where IV can't be manipulated - due to ethical/practical reasons

  +can have high ecological validity - allows psychologists to study effect on 'real' problems e.g. effects of disaster on mental health
• Natural experiments (limitations)

  -lack of causal relationship - because IV isn't manipulated this can't be achieved

  -lack of random allocations - as IV occurs naturally, participants can't be randomly allocated, so may be confounding variable affecting the results
• Quasi experiment (summary)

  • IV not varied by anyone, it's just a difference between people that exist e.g. gender, age
  • DV is still measured
  • no random allocation of participants to the conditions, IV is naturally occurring
  • Sherian and King (1972)
• Quasi experiment (strengths)


  +allows comparisons between types of people - no manipulation is carried out, but results show differences between people

  +can be carried out in a lab - DV can be tested in a lab, therefore high control/can be replicated
• Quasi experiment (limitations)


  -may be carried out in a lab - DV may be tested in a lab, therefore low ecological validity

  -lack of random allocations - as IV is naturally occurring, participants can't be randomly allocated, so may be uncontrolled confounding variables

  -cause and effect - difficult to ascertain