Types of experiments

• Laboratory experiment- An experiment that takes place in a controlled environment where the experimenter manipulates the IV and measures the DV
• Strengths of a lab based experiment

  • High degree of control experimenters control all variables, the IV has been precisely replicated, leading to greater accuracy.
  • Replication - researchers can repeat experiments and check results.
• Limitations of a lab based experiment

  • Experimenter’s bias- this bias can affect results and participants may be influenced by these expectations.
  • Low ecological validity high degree of control makes the situation artificial, unlike real life
• Field experiment- An experiment that takes place in a natural setting where the experimenter manipulates the IV and measures the DV
• Strengths of a Field experiment

  • Naturalistic - so more natural behaviours hence high ecological validity. Controlled IV
  • There is less likelihood of demand characteristics affecting the results, as participants may not know they are being studied. This occurs when the study is covert.
• Limitations of a Field experiment

  • Ethical considerations - invasion of privacy and likely to have been no informed consent.
  • Loss of control - over extraneous variables hence precise replication not possible.
• Natural experiment-  These are conducted in the everyday (i.e. real life) environment of the participants, but here the experimenter has no control over the IV as it occurs naturally in real life
• Strengths of a Natural experiment

  Provides opportunities for research that would have otherwise been impossible due to practical or ethical reasons.

  High external validity- as you are dealing with real life issues.
• Limitations of a Natural experiment

  • They may be more expensive and time consuming than lab experiments.
  • There is no control over extraneous variables that might bias the results. This makes it difficult for another researcher to replicate the study in exactly the same way.
• Quasi experiments- those where the change in IV cannot be manipulated or randomly assigned (i.e: male/female, young/old)
• Strengths of a Quasi experiment

  • Due to the IV naturally occurring within the individual it may be more reflective to that individual.
  • They allow researchers to investigate variables that would be unethical to manipulate
• Limitations of a Quasi experiment

  • Control over extraneous variables is often difficult. As the researcher is not manipulating the IV, they can be less sure that it caused an EFFECT on the DV.
  • They are generally hard to replicate and therefore can lack internal and external reliability.