Experiments

• What are the key features of an experiment?

  1. IV is manipulated by experimenter
  2. Participants are randomly assigned to groups
  3. Attempt to control all extraneous variables
• What are the four types of experiments?

  • Lab experiment
  • Field experiment
  • Natural experiment
  • Quasi experiment
• What are the features of a lab experiment?

  • Control of extraneous variables
  • Manipulation of IV
  • Random assignment of participants
  • Replicable
  • Artificial setting
• What are the features of a field experiment?

  • Controlled environment
  • Manipulation of IV
  • Real life setting
• What are the features of a natural experiment?

  • Limited control over the independent variable
  • Naturally occurring
• What are the features of a quasi experiment?

  • IV is a feature of the participant -> non-random assignment
  • e.g. age, gender
  • Lack full control over variables
  • May not have a control group
• What are the strengths of a lab experiment?

  • Well-controlled
  • High internal validity
  • Precision
  • Easily replicable
  • Can establish causal relationship
• What are the strengths of a field experiment?

  • Controlled
  • Less artificial - high mundane realism
  • High ecological validity
  • Ability to establish causality
• What are the strengths of a natural experiment?

  • Allows unethical research to happen
  • Enables studies of real-world problems
  • High mundane realism
  • High ecological validity
  • Causal inference
• What are the strengths of a quasi experiment?

  • Control over variables
  • Allows comparison between different characteristics of people
  • Ability to study cause and effect relationships
  • Practicality
• What are the weaknesses of a lab experiment?

  • Artificial environment
  • Low ecological validity
  • Demand characteristics
  • Lack mundane realism
• What are the weaknesses of a field experiment?

  • Limited control over extraneous variables
  • Low internal validity
  • More time-consuming and expensive
• What are the weaknesses of a natural and quasi experiment?

  Natural: Lack of control, potential confounding variables (low internal validity), cannot demonstrate causal relationships, conditions have to vary naturally Quasi: Limited generalisability, potential selection bias, random allocations not possible, demand characteristics

  • Both natural and quasi share weaknesses
• What is an example of a lab experiment?

  Loftus and Palmer -> eyewitness testimony

  • Conducted in laboratory
• What is an example of a field experiment?

  Bickman -> uniform, obedience

  • Conducted in streets of New York
• What is an example of a natural experiment?

  Rutter -> Romanian orphans

  • Conducted through English and Romanian adoptee (ERA) study, would not have happened if Romanian children were not adopted into UK families
• What is an example of a quasi experiment?

  Jacobs -> age affecting capacity of STM

  • Age is a present characteristic of all participants