Types of experiments

• Laboratory experiment

  = An experiment that takes place in a controlled environment within which the researcher manipulates the IV and records the effect on the DV.

  • Control extraneous variables
• Strengths of laboratory experiment

  • Control over confounding variables and extraneous variables.
  • Researcher can ensure that any effect on the dependent variable is likely to be the result of manipulation of the independent variables, so cause and effect relationships are shown. Has high internal validity.
  • Replication is possible because of the high level of control.
• Limitation of laboratory experiments

  • Lack generalisability, the experiment is artificial and not like everyday life so has low external validity.
  • Participants are aware they are being studied so may show demand characteristics.
  • Low mundane realism, doesn't represent everyday experience.
• Field experiment

  = An experiment that takes place in a natural setting within which the researcher manipulates the IV and records the effect on the DV.
• Strengths of a field experiment

  • High mundane realism as the environment is more natural.
  • May produce behaviour that is more valid
  • High external validity
• Limitations of field experiments

  • Loss of control over confounding and extraneous variables.
  • So cause and effect relationships are more difficult to establish.
  • Replication not always possible.
  • Ethical issues if the participant isn't aware they are being studied they may not have given consent.
• Natural experiment

  = An experiment where the change in the IV is pre-existing.

  Researcher records the effect on the DV.
• Strengths of a natural experiment

  • High external validity as they involve more real life problems.
  • Provide opportunities for research.
• Limitations of natural experiment

  • A naturally occuring event may happen rarely, reducing research opportunities.
  • Participants may not be randomly allocated to conditions so researcher may be less sure whether the IV effected the DV.
  • Research may be conducted in a lab so may lack realism and involve demand characteristics.
• Quasi experiment

  = Have and IV based on an existing difference between people.

  • The IV is not manipulated.
• Strengths of quasi experiment

  • Controlled conditions so high internal validity, replication is possible.
• Limitations of quasi experiments

  • May be confounding variables as random allocation is not possible.
  • The IV is not deliberately changed so we cant say the IV has caused any observable change.