Types of experiments

• What are laboratory experiments?

  • Conducted in highly controlled environments.
  • Doesn’t always have to be a lab, could be a well-controlled classroom.
• Strengths of the laboratory experiments

  • High control over confounding and extraneous variables, meaning the researcher can ensure that any effect on the DV is likely to be the result of the IV, thus high internal validity.
  • Can be more easily replicated as there is greater control and less of a chance for new extraneous variables, meaning the findings can be confirmed supporting the validity.
• Limitations of laboratory experiments

  • May lack generalisability as the controlled environment may be artificial and real-life behaviours can’t always be generalised, therefore there is low external validity.
  • Demand characteristics may be a problem as the cues invite a particular response from participants, meaning the findings may be due to the cues rather than the IV.
• What are field experiments?

  • In a natural, more everyday setting.
  • Researcher goes to the participants’ usual environment.
• Strengths of field experiments

  • Conducted in a more natural environment so participants‘ behaviour is more authentic and valid, therefore results may be more generalisable to everyday life.
  • Participants may be unaware they are being studied due to being in their natural environment, meaning they are more likely to behave normally, therefore the study has greater external validity.
• Limitations of field experiments

  • It’s more difficult to control the CVs and EVs, meaning the changes in the DV may not be due to the IV, so its more difficult to establish cause and effect.
  • There are ethical issues as the participants in the field experiment may not have given informed consent, therefore it is an invasion of the participants’ privacy.
• What is natural experiments?

  The experimenter doesn’t manipulate the IV.
• Strengths of field experiments

  • May be the only practical and ethical option as it can be seen as manipulating the IV as unethical.
  • There is greater external validity as natural experiments involve real-world issues, meaning they findings are more relevant to real experiences.
• Limitations of natural experiments

  • The natural event may only occur rarely which reduces the opportunities for research, meaning it can limit the opportunity to generalise findings.
  • Participants aren’t randomly allocated, so the researcher is less unsure whether the IV affected the DV, therefore demand characteristics may be an issue.
• What are quasi-experiments?

  • The IV is based on a pre-existing difference between people.
  • The IV can’t change.
• Strengths of quasi-experiments

  • There is high control as they are often carried out under controlled condition, meaning replication is possible.
  • Comparisons can be made between people.
• Limitations of quasi-experiments

  • Participants aren’t randomly allocated so there may be confounding variables.
  • The IV is not deliberately changed by the researcher so we can’t be certain that the IV has caused any change.