Experimental Variables Flashcards
What are the main features of the correlational method?
- Two variables are observed naturally
* Quantifies the strength and direction of relationship
What is the main disadvantage of correlational studies?
They are only correlational and hence cannot confirm cause and effect
What are experiments characterised by?
- An experimenter systematically varies the independent variable(s) to see the effects on the dependent variable.
- The experimenter controls the effects of other variables
- Investigates cause and effect relationships
- Random assignment of participants
What is the difference between an experiment and a quasi-experiment?
- An experiment has random assignment of participants to the different conditions.
- This is normally not possible in a quasi-experiment due to the studies being on particular illnesses or about other variables that cannot be randomly assigned.
What is the main disadvantage of the experimental method?
It is difficult to control for all confounding variables.
What is an extraneous variable?
Extraneous variables are those that could affect the dependent variable and must be controlled.
What is considered to be a confounding variable?
A confounding variable is an unmeasured third variable that influences, or “confounds,” the relationship between an independent and a dependent variable by suggesting the presence of a spurious correlation.
When an extraneous variable has not been properly controlled and interferes with the dependent variable (i.e. results) it is called a confounding variable.
What is the independent variable?
It is the variable which is actively varied by the experimenter. It is also known as the treatment or a factor.
What does it mean when an Independent variable has levels?
These are the experimental conditions:
For example - say the experiment is on memory recall ability while music is playing. There are then 3 groups, one with no music, one with classical music and one with heavy metal. Therefore, there is one independent variable, with 3 levels.
No music vs classical vs heavy metal
What are the basic principles for controlling extraneous variables?
- Build them into study design
- Random assignment
- Matching of participants according to EV
- Blinded procedures
What is the dependent variable?
It is the variable for which the effect of the independent variable is registered.
What are the two kinds of spurious correlations in observational studies?
- Common cause - a third variable causes both A and B
* Coincidence - A and B just happen to occur together
What is a moderator variable?
It influences the strength of the relationship between the IV and DV.
What is a mediator variable?
It explains the effect of the IV on the DV. Therefore the effects of the IV flow through the mediator variable, which then effects the DV.
