Experimental Methods Flashcards
(14 cards)
Variables
Independent (experimental) variable: variable that is manipulated in order to determine its effects on dependent v.
Control condition: provides standard against which experimental conditions can be compared where IV is not manipulated.
Dependent variable: variable bring measured.
Extraneous variable: variables that COULD affect DV.
Confounding variables: variables that HAVE affected DV.
Operationalisation
Dependent and Independent variables need to be operationalised.
Operationalisation is defining the variables in such a way as to make them measurable.
Laboratory experiment
- Carried out in a controlled environment, allowing the researcher to exert a high level of control over the IV and eliminate any EV.
- Participants are randomly allocated to a condition.
- Conducted in an artificial setting.
Laboratory experiment: Advantage
- Very high level of control so it’s easy to control for any Extr. variables and prevent them from becoming Conf. variables.
- As researcher can manipulate IV, they can establish a cause and effect relationship between IV and DV.
- Easily replicated by other researchers to see if similar results are obtained. If findings are similar then results are reliable.
Laboratory experiment: Disadvantage
- Strong chance of demand characteristics as participants might guess what the aim of the study is and change their behaviour accordingly = data invalid. Some behave more positively because of SOCIALLY DESIRABILITY BIAS.
- By having high level of control over IV and extr. variables, the experiment can lack mundane realist so the study doesn’t have ecological validity (ability to generalise findings).
Field experiments
Experiment carried out in the real world or in natural setting. IV is manipulated to see effect on DV.
Field experiment: Advantages
- More mundane realism and ecological validity than lab.
- Cause and effect can be determined as IV is manipulated and DV is observed.
- Less chance of demand characteristics so more valid data.
Field experiment: Disadvantages
- Less control over extraneous variables so effect on DV may not be caused by IV but by these EV. Research not valid.
- Less control over the sample (people taking part).
- More difficult to replicate.
Natural experiments
Researcher takes advantage of a naturally occurring independent variable to see its effect on DV.
Natural experiments: Advantages
- High level of mundane realism and ecological validity,
- Useful when it is impossible or unethical to manipulate IV or sample in a lab or field experiment.
E.g group of naturally stressed men with high levels of stress and cholesterol.
Natural experiments: Disadvantages
- Low level of control over extraneous var.
- Difficult to replicate.
- Difficult to determine cause and effect due to low levels of control.
Quasi Experiment
Contain a naturally occurring IV. However, in a quasi-experiment the naturally occurring independent variable is a difference between people that already exist.
Researcher examines effect of this variable on DV.
Quasi experiment: Advantages
- High level of control; effect of extraneous variables are minimised, so experimenter can be more confident that is the IV which has affected the DV.
- Replication is very likely. Due to strict controls this means it is easier to replicate and test reliability.
Quasi experiment: Disadvantages
- Lack of ecological validity as experiment is artificial.
- Demand characteristics can occur; making data invalid.
