Types of experiments

• Lab experiments key features

  • IV is manipulated by the researcher
  • Participants can be randomly allocated to conditions
  • Cause and effect can be established
  • In an artificial environment so extraneous variables are easy to control
  • Participants typically know they're in a study
• Advantage of lab experiments

  Easy to replicate.

  This is because its in an artificial environment which is highly controlled and use a standardised procedure.

  This is a strength because the study can be repeated, and reliability/validity of the results can be checked.
• Disadvantage of lab experiments

  Increased risk of demand characteristics.

  This is because participants know they're in a study and so may look for clues in the research about how to behave and change their natural behaviour.

  This is a limitation because it will reduce the experiments internal validity.
• Natural experiments key features

  • IV isn't manipulated by the researcher
  • Participants can't be randomly allocated to conditions making participant variables difficult to control.
  • Cause and effect cannot be established
  • In a more natural, everyday setting or controlled laboratory so situational extraneous variables are only controlled when its in a laboratory setting.
  • Participants typically know they're in a study.
• Advantages of natural experiments

  High external validity.

  This is because they investigate a real-life issue that the participants have experienced in their everyday lives, and can take place in a natural setting.

  This is a strength because it increases the extent to which the results can be generalised.
• Disadvantage of natural experiments

  Hard to replicate.

  This is because the IV isn't manipulated by the researcher, it has occurred naturally over time and may be a one-off event.

  This is a limitation because the research cannot be repeated, and reliability/validity of the results cannot be checked.
• Field experiment key features

  • IV is manipulated by the researcher
  • Participants can be randomly allocated to conditions controlling the effect of participant variables
  • Cause and effect can be established
  • In the participants natural, everyday environment so situational extraneous variables are not easy to control
  • Participants typically don't know they're in a study.
• Advantage of field experiments

  Has realism.

  This is because they're in the participants natural environment, with a task that resembles an everyday task. Therefore, they're more likely to show natural behaviour.

  This is a strength because as participants are likely to show their natural behaviour it increases the study’s external validity - easier to generalise.
• Disadvantage of field experiments

  Raises ethical issues.

  This is because participants are unaware they're in a study.

  This is a limitation because it is the right of the participant to give informed consent, have the right to withdraw and to not be deceived.
• Quasi experiments key features

  • IV isn't manipulated by the researcher, IV is based on a pre-existing difference between people
  • Participants can't be randomly allocated to conditions so participant variables are difficult to control.
  • Cause and effect harder to establish
  • Typically in a controlled lab setting, but can be in a natural, everyday setting so situational extraneous variables can only be controlled when in a lab setting
  • Participants typically know they're in a study
• Advantage of a quasi experiment

  Ease of replication.

  This is because they're usually in an artificial environment, highly controlled and uses a standardised procedure.

  This is a strength because the study can be repeated, and reliability/validity of the results can be checked.
• Disadvantage of a quasi experiment

  Difficult in controlling participant variables.

  This is because the IV is based on a pre-existing difference between people, therefore they can't be randomly allocated to conditions.

  This is a limitation because these participant variables may affect the results, reducing the study’s internal validity.