Types of Experiments

• Lab Experiments


  • highly controlled
  • artificial environment
  • IV is manipulated and the DV is measured
• participants


  people being tested in the experiments
• field experiments


  • natural environment
  • IV still manipulated
  • participants not aware they're being studied
• Natural Experiments 


  • natural/lab environment
  • IV not directly manipulated (due to ethical issues)
  • IV is naturally occurring
• Quasi Experiments


  • lab or natural environment
  • Iv not manipulated, it just exists, based on differences between people (age, gender)
• Internal Reliability


  a measure of consistency within itself, such as whether the questions in a questionnaire are all measuring the same thing
• External Reliability


  assesses consistency when different measures of the same thing are compared

  This can be improved by using standardised procedures.
• Internal Validity 


  Extent to which the observed effect was due to experimental manipulation rather than other factors
• External Validity 


  Extent to which research findings can be generalised beyond research; to other settings (ecological), other people (population validity) and over time (historical validity)
• Natural Experiments- Strengths 


  • Increased mundane realism and ecological validity
  • Psychologist can study real problems
  • study factors that can't otherwise be studied due to ethical or practical reasons.
• Natural Experiments- Limitations


  • Can't demonstrate casual relationships as IV not directly manipulated.
  • Random allocation not available
  • May not be able to control all confounding variables
  • May limit internal validity
• Quasi Experiments- Strengths


  • Allows for comparison between groups/different types of people.
• Quasi Experiments- Limitations


  • Can only be used when conditions occur naturally.
  • Participant may be aware of the study, reducing internal validity.
  • DV may have an artificial task, reducing ecological validity and mundane realism.
• Mundane Realism

  whether a study (and tasks within it) mimic the real world.
• Demand Characteristics


  cues that may make participants aware of the true nature of the study or what the researcher expects, this may alter the participants behaviours
• Lab Experiment- Strengths 


  • well controlled
  • Extraneous variables are minimised, thus higher internal validity.
  • Easy replicable- external validity.
• Lab Experiments- Limitations


  • materials may lack mundane realism
  • participants may not behave naturally leading to lower ecological validity.
• Field Experiments- Strengths


  • Less Artificial, higher mundane realism, higher ecological validity
  • Participants not aware of the study
• Field Experiments- Limitations


  • Less control over extraneous variables, reduces internal validity.
  • Time consuming
  • expensive