Types of experiment

• Laboratory experiment: Definition

  Investigates differences between conditions under controlled settings. Participants are aware that they are in a study but may not know the true nature of the study. They are randomly allocated to conditions.
• Laboratory experiment: Advantages

  High control, leading to accuracy and objectivity- cause and effect- manipulation is the cause- as a result of control.

  Replication
• Laboratory experiment: Disadvantages

  Investigator effects and demand characteristics.

  Operationalised IV + DV, too narrowing.

  Lacks ecological validity- not a real life setting- result of high control and unrealistic consequences.
• Field experiment: Definition

  Where experiments are carried out in a natural setting- IV is manipulated. They can be carried out in schools, playgrounds , factories, hospitals and anywhere where people live or work.
• Field experiment: Example

  Bickman (1974) studied compliance. Researchers dressed casually or in uniforms and asked passers-by to pink up litter or give a coin to a stranger.
• Field experiment: Advantages

  Ecological validity- carried out in real-life setting

  Less demand characteristics
• Field experiment: Disadvantages

  Extraneous variables are difficult to control- therefore unsure if IV actually affects DV.

  Less control means they're difficult to replicate- the same people cannot be tested.

  Ethical issues- no informed consent
• Natural experiment: Definition

  Naturally varying IV are investigated. The IV is not manipulated by the researcher (e.g. introducing TV to a pacific island, attending private or state school).
• Natural experiment: Advantages

  Allws the experimenter to study effects of an IV that could not be ethically manipulated.

  Behaviour is likely to be representative as it is carried out in real life situations.

  Demand characteristics is not a problem.
• Natural experiment: Disadvantages

  Cause and effect relationship difficult to ascertain- due to little control over IV (other variables impact the experiment).
• Quasi experiment

  True experiments involve the manipulation of the IV by an experimenter to observe the effect on the DV. So therefore, natural experiments are not 'true experiments'. Such experiments are sometimes called quasi experiments instead. Naturally occurring IV where participants cannot be randomly assigned to groups- they just are in the conditions (e.g. gender, mental disorders, eye colours etc...)
• Quasi experiments do not have experimental design.