Types of experiment:

• What are the four types of experiment?

  1. Laboratory experiment
  2. Field experiment
  3. Natural experiment
  4. Quasi- experiment
• Laboratory experiment:

  • A lab experiment is an experiment carried out in a controlled lab setting
  • The researcher will manipulate the IV and measure the DV in the lab
  • The ppts will be aware that they are being tested
• What are the strengths of doing a lab experiment?

  • Easier to control extraneous variables and prevent them from becoming confounding variables. This means that cause and effect can be established and internal validity is high
  • Can be easily replicated by other researchers. This means that the external reliability of the findings can be established
• What are the limitations of doing a lab experiment?

  • A laboratory is an artificial environment. This means that ecological validity is low.
  • Ppts are always aware that they are being tested. This means that demand characteristics are likely to act as an extraneous variable.
• Field experiments:

  • A field experiment is an experiment carried out in a real-life setting such as a hospital or school
  • The researcher will manipulate the IV and measure the DV in the natural setting
  • The ppts may not be aware that they are being tested
• What are the strengths of doing a field experiment?

  • Research takes place in a natural environment. This means that ecological validity is high
  • Ppts may not be aware that they are being tested. This means that demand characteristics are less likely to act as an extraneous variable.
• What are the limitations of doing a field experiment?

  • Difficult to control extraneous variables and prevent the from becoming confounding variables. This means that cause and effect cannot be established and internal validity is low.
  • Difficult for other researchers to replicate the research. This means that the external reliability of the findings cannot be established.
• Natural experiment:

  • A natural experiment is an experiment in which the researcher has not manipulated the IV directly
  • Instead, the researcher makes use of naturally occurring differences in the IV
  • The DV is usually measured in the laboratory
  • PPts are therefore usually aware that they are being tested
• What are strengths of doing a natural experiment?

  • Researchers study naturally occurring situations. This means that ecological validity is high.
• What are limitations of a natural experiment?

  • As the researcher does not directly control the IV, it is difficult to control extraneous variables and prevent them from becoming confounding variables. This means that cause and effect cannot be established and internal validity is low.
  • The naturally occurring situation that the researcher wants to study may only occur rarely, thus reducing the available opportunities for research.
• Quasi experiments:

  • A quasi- experiment is an experiment in which it is not possible for the researcher to manipulate the IV directly because it is based upon an existing difference between people
  • For example, gender, age, or whether an individual suffers from a psychological disorder or not
  • Instead, the researcher makes use of naturally occurring differences between people
  • The DV is usually measured in the laboratory
  • Ppts are therefore usually aware that they are being tested
• What are strengths of doing a Quasi experiment?

  • Researchers study naturally occurring differences between people. This means that ecological validity is high.
• What are limitations of doing a Quasi experiment?

  • As the researcher does not directly control the IV, it is difficult to control extraneous variables and prevent them from becoming confounding variables. This means that cause and effect cannot be established and internal validity is low
  • Ppts cannot be randomly assigned to conditions. This means that ppts variables are likely to act as an extraneous variable.