Types of experiment

• What are the 4 types of experiment?

  • Laboratory (L)
  • Field (F)
  • Natural (N)
  • Quasi (Q)
• What are laboratory experiments?

  • Conducted in deliberately constructed and controlled environment
  • Independent variable is manipulated by the experimenter
  • Dependent variable is measured
  • Extraneous variables are controlled
  • Participants are randomly allocated to each condition
  • Participants know they are in a study as they have come along to the lab to take part
• What are field experiments?

  • Experiment is conducted in the 'field' - a real life setting for the individuals involved. In the kind of environment where they would likely display the type of behaviour being studied
  • Independent variable is still manipulated by the experimenter and dependent variable measured; extraneous variables will be less controlled (as experimenter doesn't have control of the environment)
  • Participants are often unaware they are in the research
• What are quasi experiments?

  • Can take place in a laboratory or in a real life setting but is not possible to randomly allocate participants to a condition
  • Independent variable is a pre-existing feature of the participants themselves, so they are automatically assigned to a particular condition due to a characteristic they have e.g. age
  • Researcher does not manipulate the independent variable
  • Features of participants don't change so they can only take part in one condition, therefore can only be undertaken as an independent measures design
• What are natural experiments?

  • Independent variable is a naturally occurring event - the researchers take advantage of it happening
  • Dependent variable is measured by researchers but independent variable is not set up by then
  • Participants often unaware they are taking part
  • Involves studying behaviour before and after a change occurs
• What are the strengths of laboratory experiments?

  • High level of control of extraneous variables, situational and possibly participant so can be certain that nothing else affects the DV than the IV
  • Means that cause and effect can be established
  • Can be easily replicated so can check reliability of the study
• What are weaknesses of laboratory experiments?

  • Lacks ecological validity and mundane realism due to the artificial setting which means it's difficult to generalise findings to real life behaviour
  • More likely to cause demand characteristics/social desirability bias as participants clearly know they are in a study
• What are strengths of field experiments?

  • High ecological validity and mundane realism as in a natural setting meaning findings can be generalised to real life behaviour
  • Can reduce chance of participant effects (e.g. demand characteristics and social desirability bias) if people don't know they are taking part, making the study more valid
• What are the weaknesses of field experiments?

  • Less control of situational variables, so less confidence in cause and effect relationship established between IV and DV
  • Less easy to replicate because the environmental conditions will not be the same again; makes it hard to check reliability
  • Could be ethical issues due to a lack of informed consent, right to withdraw and so on
• What are the strengths of natural experiments?

  • Increased ecological validity as it takes place in a natural setting
  • Can reduce participant effects (sometimes) like demand characteristics/SDB if participants do not know they are taking part
  • Allows us to study the impact of unique events that we couldn't create in a lab due to practical and ethical conditions
• What are the weaknesses of natural experiments?

  • Less control of extraneous variables (participant and situational) making us less confident about any possible cause and effect relationship (lower internal validity)
  • Very unlikely to be able to replicate study so difficult to assess reliability
• What is the strength of a quasi experiment?

  • Useful when it's unethical to manipulate the IV (e.g. gender, age can't be manipulated by researcher)
• What are the weaknesses of quasi experiments?

  • More chance of extraneous variables, especially participant variables, as participants are not randomly assigned to each condition
  • Have to wait for the IV/ search for candidates who fit the description of the IV they want to research as the IV is a naturally occurring characteristic