Methods Flashcards
Are correlations a method
No, they are a way of analysing a set of data
What type of variables are used in a correlation
Co-variables
THERE IS NO DEPENDENT/INDEPENDENT VARIABLE
What is a co-variable
One of the two variables you measure in a correlation
What is a positive correlation
Both co-variables will change in the same direction
From above zero up to one
What is a negative correlation
Where the co-variables change in different directions
What type of diagram/graph is used to illustrate a correlation
Scatter graph
What are the strengths of a correlation
Useful when unable to manipulate due to ethical reasons
Useful for initial investigation
Rely on quantitative data which is easy to replace increasing reliability
What are the weaknesses of a correlation
- Do not show a causal relationship
- Hidden/Intervening variables could affect the co-variable
- Uses quantitative data so may lack validity
- Issue with direction of causality
What is the lack of direction of causality with a correlation
The two co-variables are linked but the direction is not clear.
You cannot tell which is effecting the other
What is a hidden variable
Where there is no direct link between the two co-variables
However a third variable has an effect on both independently
So as the third variable increases/decreases it causes the co-variables to increase/decrease but the two co-variables do not directly have an effect on each other
What is an intervening variable
Where co-variable 1 has no direct effect on co-variable 2
But does effect variable 3 which in turn has an effect on variable 2
1->3->2
But 1 doesn’t effect 2 directly
What is needed to use a spearmans rho test
Correlation
Ordinal data
Test of association
Different types of brain scans
PET
CAT
fMRI
What does a PET scan show and how does it work
Brain function, red areas = high activity, blue areas = low activity
Pp is injected with radioactive glucose The pp then performs a task As brain works tracer breaks down causing gamma rays to be released Which are detected by a scanner Lots of gamma rays = lots of activity
What does an fMRI scan show and how does it work
Brain function
Pp place their head in a large electromagnet
As neural activity increases there is an increase in blood flow to more active areas, as the brain needs more O2 there
Hb in blood repels magnetic field when it has O2
When it releases O2 it will follow the direction of the magnetic field
Creating a map of activation showing changing levels of neural activity