types of experiments

• types of experiments:

  1. laboratory experiments
  2. field experiments
  3. quasi experiments
  4. Natural experiments
• what is a laboratory experiment?

  an experiment where the independent variable is manipulated in an artificial, controlled environment.
• strengths and weaknesses:

  strengths

  • high control over extraneous variables meaning high internal validity
  • --> can establish cause and effect relationship

  weaknesses

  • low ecological validity
  • low external validity
• what is a field experiment?

  when the IV is manipulated in a natural, everyday setting
• what is a quasi experiment?

  when the researcher cannot manipulate the IV in an experiment- it's already the personal characteristic of the participant
• strengths and weaknesses of Quasi Experiments

  strengths:

  • enable researchers to study independent variables that can’t be studied in laboratory or field experiments.

  weaknesses:

  • A con is that participants can’t be randomly allocated to groups, meaning that uncontrolled participant variables might act as confounding variables.
  • A con is that the study may lack internal validity making it harder to establish cause and effect
• what is a natural experiment?

  An experiment where the independent variable is an event that has already happened.

  An experiment where the independent variable isn’t manipulated and can’t be randomly allocated.
• strengths and weaknesses of Natural Experiments

  strengths:

  • enables researchers to study independent variables that it would be unethical or impractical to investigate in a laboratory or field experiment.

  weaknesses:

  •  difficult to establish a cause and effect relationship between the independent variable and the dependent variable.
  • natural experiments is that the researchers have little control over extraneous variables so the study has low internal validity.
• what types of experiments do researchers have to assign experimental designs for?

  laboratory and field experiments
• what is matched pairs design?

  when the researchers  match the participants from the control and experimental groups for a particular participant variable
• independent groups design is…

  When the researcher allocates different participants to each group but don’t match the participants for any particular variables.
• Repeated measures design is….

  when the same participants take part in all of the experimental conditions.
• Repeated Measures: Limitations

  the results can be influenced by order effects: which is when the order of the experimental conditions influences the results of a study.

  participants are more likely to respond to demand characteristics when they repeat the same task multiple times.
• counterbalancing

  A way of preventing order effects from influencing results.

  When in a repeated measures design, different participants are made to take part in the experimental conditions in different orders