Types of Experiment

• Laboratory experiments


  Experiments conducted in a lab, a highly controlled environment; advantage of being easily controlled
• Strengths of laboratory experiments

  - High internal validity; allow for the precise control of variables.

  - IV is manipulated so allows cause-effect relationships (causality) to be established.

  - Easier to replicate; so other researchers can see if they obtain similar results (good reliability).

  - Use of technical apparatus which cannot be used in more natural settings to take accurate measurement, objective and scientific.
• Limitations of laboratory experiments

  - Low ecological validity/mundane realism - has been conducted in an artificial environment which may produce unnatural behaviour that does not reflect real life.

  - This means the results cannot be generalised to real life.

  - Demand characteristics/experimenter effects may affect the results and become confounding variables.
• Field experiments


  Experiments conducted in natural settings rather than in the laboratory
• Strengths of field experiments

  - Participants are more likely to behave in a typical way, less risk of demand characteristics.

  - Higher ecological validity as in natural setting.
• Limitations of field experiments

  - Low internal validity; risk of confounding variables.

  - Easier to collect large amounts of data in a Lab.

  - Not possible to carry out certain types of studies in field because bulky equipment would give the game away.

  - Ethical issues; consent.

  - Causality cannot be established due to uncontrollable extraneous variables.
• Natural experiments


  Naturally occurring events or phenomena having somewhat different conditions that can be compared with almost as much rigor as in experiments where the investigator manipulates the conditions.
• Strengths of natural experiments

  - Allows study of the effects of an independent variable that may be difficult or unethical to manipulate.

  - May have good practical applications in the real world.
• Limitations of natural experiments

  - Can't be precisely replicated.

  - Naturally occurring event may happen rarely and limit generalisation of findings to similar situations.
• Quasi-experiments


  Comparisons of groups that differ in exposure to a variable of interest that cannot be manipulated for ethical or practical reasons
• Strengths of quasi-experiments


  Allows study of an independent variable that cannot be manipulated and may well have good practical applications in the real world.
• Limitations of quasi-experiments


  Can't randomly allocate Ps to conditions and therefore there may be a confounding variable.