Lesson 1: Experimental Methods Flashcards
Independent variable
Variable that is changed to determine its effect on the dependent variable. The independent variable may be divided into levels, sometimes referred to as experimental conditions.
Dependent variable
Variable being measured
Extraneous variable
any variables other than the IV that affect the DV
Confounding variables
Any variables (other than the IV) that HAVE affected the DV e.g. include light and noise
Operationalisation
- to have a successful experiment, the DV and IV must be operationalised
- therefore they must be defined and stated how it will be measured
- e.g. aggression means… and can be measured by displays of verbal or physical acts of aggression in a 10 minute period
Laboratory experiment
When an experiment is carried out in a controlled environment (artificial setting), such as a laboratory, allowing the researcher to exert a high level of control over the IV and eliminate any EV.
- researcher can observe and measure the change in DV caused by their manipulation of IV
- pps are randomly allocated to a condition
- aim of controlling EVs is to minimal their possible impact on the results of the investigation
Advantages of laboratory experiments
- high level of control over the IV and conditions, therefore it is easy to control any extraneous variable and prevent them from affecting the data
- researcher can manipulate the IV and establish a cause and effect relationship between the independent variable and the DV
- can be easily replicated by other researcher
Disadvantages of lab experiments
- social desirability bias i.e. demand characteristics
- can lack mundane realism and therefore the study may not have ecological validity due to high control of IV and EVs
Field experiments
An experiment carried out in the real world or in a natural setting rather than in an artificial setting of a laboratory.
- independent variable is still controlled by the researcher to see the effect on the dependent variable
- e.g. observe people on the street
Advantages of field experiments
- more mundane realism and therefore ecological validity than in a lab
- researcher can manipulate the IV and establish a cause and effect relationship between the IV and DV
- less chance of demand characteristics as pps might not even be aware that they are taking part in research so they will behave more naturally
Disadvantages of field experiments
- less control over extraneous variables compared to lab therefore the effect on the DV may not be caused by the IV so research may not be valid
- less control over the sample so sample may not be representative of the population
- may be difficult to reproduce which means they can be unreliable compared to lab experiments
Natural experiments
Researcher takes advantage of a naturally occurring IV to see its effect on the dependent variable.
- measures variables that aren’t directly caused by the experimenter e.g. behaviour in a single-sex and mixed school
- means IV is naturally occurring
Advantages of natural experiments
- high level of mundane realism and ecological validity compared to lab experiments
- they are very useful when it is unethical to manipulate the IV in a lab or field experiment
- e.g. psychologists may wish to study a naturally occurring event which would otherwise be unethical to impose e.g. a group of naturally stressed men at 65 who have high cholesterol and stress levels
Disadvantages of natural experiments
- low control over extraneous variables compared to lab experiment
- very difficult to reproduce so are often unreliable
- difficult to determine cause and effect due to low levels of control
Quasi experiments
Contain a naturally occurring IV. However, the naturally occurring IV is a difference between people that already exists i.e. gender and age. The researcher examines the effect of this variable on the dependent variable.
