Biological Approach - Research Methods Flashcards
What does a correlation look for?
A relationship between two variables.
What is a positive correlation?
When one variable increases so does the other.
What is a negative correlation?
When one variable increases the other decreases.
What type of graph are correlations shown on?
Scatter graph
What is the value of a perfect positive correlation/
+1
What is the value of a perfect negative correlation?
-1
What direction does a positive correlation create?
/
Up from left to right
What direction does a negative correlation create?
\
Down from left to right
What are the 4 levels of measurement/types of data?
Nominal
Ordinal
Interval
Ratio
What is Nominal data?
Most basic level of measurement
Used when data is put into tally charts/categories
Only tells us how many ppts picked each option
Doesn’t give an individual score for each ppts
What is Ordinal data?
Used when data can be ordered eg 1st, 2nd, 3rd
Can’t tell the gap between 1st and 2nd etc
Always used with questionnaires
Gives us an individual score for each ppts
What is Interval data?
The distance between each score has a meaning and equal value.
eg gap between 5-10cm is same as 20-25cm
0 is just another number on the scale, it does not mean there is nothing
eg 0 degrees c doesn’t mean there’s no temperature
What is Ratio data?
The distance between each score has meaning and an equal value.
However, 0 does mean nothing.
eg 0 seconds to do something means it took no time
What is a Type 1 error?
If you reject the null hypothesis and it is actually true
Happens when the level of significance is too lenient
What is a Type 2 error?
If you keep the null hypothesis when your experiment did work. (when there is a significant difference)
Happen when the level of significance is too harsh
What level of probability do we start at?
p <= 0.05
The probability the results are due to chance is equal to or less than 5%
(unless we’re trying to disprove someone else’s results. Then we start at p <= 0.01)
What test do we use on correlations?
Spearman’s rho
Strengths of correlation
- Useful as a preliminary research techniques, allowing a link to be identified that can be further investigated.
- Can be used for sensitive topics as no deliberate manipulation of variables is required.
Weaknesses of correlation
- Correlations only identify a link, they don’t identify which variables causes which. A 3rd variable may be influencing the results that’s not considered.
- Lack of correlation may not mean there is no relationship, it could be non-linear.
What are the 3 scanning methods?
CAT
PET
fMRI
Describe a CAT scan
- Uses X-rays to take images of the brain
- person lays on a bed that slowly moves through the gantry.
- The x-ray source rotates around the gantry (Circular machine).
- After every full rotation a 2D slice image is formed, then the gantry moves slightly forward and it is repeated.
- After it is done, all images are fitted together to create a 3D image of the brain.
Describe a PET scan
- Takes functional images of the brain
- A radioactive tracer attached to glucose is injected into the person.
- Needs to wait for the tracer to be absorbed.
- Areas that are most used will absorb more glucose/tracer.
- Person is on a bed in the PET scanner that slowly moves through it.
- Positrons are emitted due to the breakdown of the tracer, these emit gamma rays that are detected by the scanner.
- 3D image is created
Describe a fMRI scan
- Uses a powerful electro-magnet focussing on blood flow
- Magnetic flow affects the magnetic nucleus of atoms and causes them to align in the same direction
- Tiny magnetic signals add up to create a signal that can be detected
- fMRI detects this blood flow and sees the more active areas, creating a functional image
Strengths of CAT scans
- Less harmful than PET scans
- Can detect changes in structure (good for tumors/haemorrhages)
- Not painful or invasive
Weaknesses of CAT scans
- fMRI gives clearer pictures
- Involves x-rays which can cause cancers
Strengths of PET scans
- Reasonably non-invasive
- measures what it intends to
- can be repeated
Weaknesses of PET scans
- Invasive due to injection
- Difficult to isolate brain functions precisely as behaviours can use multiple areas
- can be claustrophobic
Strengths of fMRI scans
- Non-invasive unlike PET
- Virtually risk-free
- Can detect small features/measurements of the brain - measured more accurately
Weaknesses of fMRI scans
- Can’t determine causation as doesn’t show the areas in the brain that are associated
- Only shows a localised area’s function not the overall communication
- Too much head movement can distort the image
