types of experiment

• Types of experiments

  • Lab experiment
  • Field experiment
  • Natural experiment
• Lab experiment


  A research method in which the experimenter manipulates one or more independent variables and measures the effects on the dependent variable under controlled conditions.
• Lab experiments

  • Conducted under highly controlled conditions (not necessarily a laboratory) where accurate measurements are possible
  • Participants are randomly allocated to each independent variable group
• Examples of lab experiments

  • Milgram's experiment on obedience
  • Loftus and Palmer's car crash study
• Strengths of lab experiments

  • Easier to replicate as a standardized procedure is used
  • Allow for precise control of extraneous and independent variables, allowing a cause-and-effect relationship to be established
• Limitations of lab experiments

  • The artificiality of the setting may produce unnatural behavior that does not reflect real life, i.e., low ecological validity
  • Demand characteristics or experimenter effects may bias the results and become confounding variables
• Field experiment

  A research method that takes place in a natural, real-world setting where the experimenter manipulates one or more independent variables and measures the effects on the dependent variable.
• Field experiments

  • Participants are unaware they are being studied, and the experimenter has less control over the extraneous variables
• Example of a field experiment


  • Holfing's hospital study on obedience
• Strengths of field experiments

  • Behavior is more likely to reflect real life because of the natural setting, i.e., higher ecological validity than a lab experiment
  • Demand characteristics are less likely to affect the results, as participants may not know they are being studied
• Limitations of field experiments

  • Less control over extraneous variables that might bias the results, making it difficult for another researcher to replicate the study in exactly the same way
• Natural experiment


  A research method in which the experimenter observes the effects of a naturally occurring event or situation on the dependent variable without manipulating any variables.
• Example of a natural experiment

  • Hodges and Tizard's attachment research (1989) compared the long-term development of children who have been adopted, fostered, or returned to their mothers with a control group of children who had spent all their lives in their biological families.
• Strengths of natural experiments

  • Behavior is more likely to reflect real life because of the natural setting, i.e., very high ecological validity
  • Demand characteristics are less likely to affect the results, as participants may not know they are being studied
  • Can be used in situations in which it would be ethically unacceptable to manipulate the independent variable
• Limitations of natural experiments

  • May be more expensive and time-consuming than lab experiments
  • There is no control over extraneous variables that might bias the results, making it difficult for another researcher to replicate the study in exactly the same way
• Types of experiments

  • Field
  • Laboratory
  • Quasi
  • Natural
• quasi experiment 


  an experiment where the IV has not been determined by the researcher as it exists naturally

  eg. gender differences studies
• strengths of quasi experiment

  controlled conditions - replicable, high internal validity
• limitations of quasi experiment

  cannot randomly allocate participants - may be confounding variables presented which makes it harder to conclude that the IV caused the DV