experiments

• Laboratory experiment

  • Controlled environment
  • Researcher manipulates the IV and records the effect on the DV
  • Strict control of extraneous variables.
• Strengths of Lab experiments

  • High control of extraneous + confounding variables (high internal validity)
  • Replication is highly possible.
  • Easy to check if results are valid and not a one off.
• Limitations of Lab experiments

  • Lacks generalisability due to the artificial environment not being able to replicate everyday life. (Low external validity and low mundane realism)
  • Demand characteristics as participants know they are being tested
• Field experiment

  • Natural environment
  • Researcher manipulates the IV and records the effect on the DV.
• Strengths of Field experiments

  • Higher mundane realism than lab due to natural environment which may produce more authentic behaviour.
  • High external validity. Especially if pp's are unaware they ar ein an experiment.
• Limitations of Field experiments

  • Lack of control over CVs and EVs which means cause and effect may be harder to establish and replication is not often possible.
  • Ethical issues if participants are unaware they are being studied due to lack of consent and privacy
• Natural experiment

  Change in IV isn't done by the researcher, would've happened even if the researcher wasn't there. Researcher records DV they decided on.
• Strengths of Natural experiments

  • High external validity as they involve studying things that are really happening. E.g. natural disasters.
  • Provide opportunities for experimenters to do research which may not normally be ethical or practical. E.g. Romanian orphan studies by Rutter et al.
• Limitations of Natural experiments

  • Naturally occurring event may be rare which may limit the generalisability of the findings.
  • Participants may not be randomly allocated therefore, researcher may unsure of causation of the DV.
• Quasi experiment


  IV hasn't been determined by anyone.Variables simply exist. E.g. old and young.
• Strengths of Quasi experiments

  • Carried out under controlled conditions. Replicable.
• Limitations of Quasi experiments

  • Cannot randomly allocate participants which means there may be confounding variables.
  • IV not deliberately changed so may not have caused the change observed.
• Independent groups

  Two separate groups experience two different conditions.Performance of the groups compared.
• Strengths of Independent groups

  • No order effects.
  • Less likely to have demand characteristics
• Limitations of Independent groups

  • High participant variables which may act as confounding variables causing validity to be reduced.
  • Less economical than repeated measures.
• Repeated measures

  All participants experience both conditions. Both conditions compared.
• Strengths of Repeated measures

  • Controls for participant variables which increases validity
  • More economical, less participants needed.
• Limitations of Repeated measures

  • Order effects - boredom, fatigue
  • Demand characteristics - work out aim.
• Matched pairs

  Participants paired together based on variables/characteristics relevant to the experiment. E.g. IQ. Each person in a pair takes part in one condition. Performance of pairs compared.
• Strengths of Matched pairs

  • No order effects, less demand characteristics.
  • Reduces participant variables.
• Limitations of Matched pairs.

  • May still be some participant variables.
  • Time-consuming, expensive.