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Statistical tests
Research aim = test for significant correlation
Participant design = correlation (NOT ---> independent, repeated or matched)
Level of measurement = ordinal or interval
Mann-Whitney U
Research aim test of significant difference for unrelated data
Participant design = independent measures
Level of measurement = ordinal or interval
Chi squared
Research aim = tests for significant difference
Participant design = independent measures
Levels of measurement = nominal
What to do before carrying out a statistical test:
1: determine the level of measurement... NOI
2: determine if the hypothesis is one tailed or two.
3: determine if this hypothesis is... a test of difference / a relationship / a correlation
4: choose a level of significance, for As ---> p < 0.05 or p < 0.01, so 1 in 20 and 1 in 100.
5: write out a null hypothesis.
6: carry out the appropriate test
7: find and use the relevant statistical table
8: check the results achieved, N or Df against the critical value.
9: for the test to be significant and the null hypothesis rejected...
Mann Whitney = value for U to be critical value
Spearman + chi = values to be critical value…read more

Slide 2

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Seeking genetic explanation: METHODOLOGY PG1
Psychologists look for genetic explanations for who we are, to try and support ideas that our behaviour
is biologically determined.
Studies on identical twins and adopted children can then be used to support or contradict this idea.
Twin studies:
Use ­ to see if behaviour is shared by those who are genetically identical.
What they use ­ concordance rates, to test if traits adopted by one twin leads to the other twin gaining the same trait, e.g. schizophrenia.
Making comparisons ­ between MZ (monozygotic twins) and DZ (dizygotic twins) by comparing concordance rates, As MZ twins share more
genes (100%) compared to DZ ( 50%). If concordance rates are higher for MZ, then genes play a strong role in behaviour.
However ­ twins share same environment, so psychologist get MZ twins who separated at birth, helps distinguish between nature vs. nurture.
1: MZ twins separated at birth, you are able to find that similarities between twins are due to genes , they share 100% genes with each other.
1: MZ twins may be treated more alike as they look identical and are of same sex. So environments aren't as controlled as they could be.
Adoption studies:
Adopted children share no genes in common with their adoptive parents, they only share the same environment.
Use ­ to separate genetic and environmental influence on behaviour.
How ­ looking for similarities in behaviour between children and biological parents or children and adopted parents
Examples ­ if child is similar to biological parents but not adoptive, then it supports ideas that genes affect behaviour.
So if child has high IQ and so do biological parents then it was the biological parents genes which determined the child's IQ
1: gives a clear view of genetic and nature effects as the genes of parents are separate from environment, similarities with bio parents = genetic
2: development trends can be studies as it can be longitudinal, so trends can be found and linked to either genes or environment.
1: MZ twins separated at birth, often share same experience growing up, agencies place them in similar home environments. So similarities
could be due to upbringing, not just genes.
2: However, twins separated at birth still share 9 months inside womb, could account for behaviour similarities.
3: lacks generalizability, number of MZ twins studies is minimal, sample sizes are small.…read more

Slide 3

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Brain scanning techniques:
Is a way that psychologists can study behaviour and the biological influences on it.
MRI ( Magnetic resonance imaging) scans:
MRI scan allows a picture of the brain to be seen, as well as the structure and whether there is damage or a cancerous tumour growing
Procedure ­ patient is placed in a large scanner, passes very strong magnetic field through head.
How it works ­ the nuclei of some atoms spin a particular way when placed in a magnet, this allows a detailed image of brain to be produced
Role of hydrogen ­ the nuclei in hydrogen molecules emit their own radio waves at a frequency that the scanner picks up.
Use of hydrogen ­ the varying hydrogen levels in the brain allow for a very detailed image of the brain to be seen.
PET (Position emission tomography) Scans:
A way of seeing the working brain, identify damage or tumours.
Procedure ­ patients injected with glucose, or water labelled with radioactive tracer, while inside scanner.
How it works ­ when the substance reaches the brain, the brain cells take it up and the tracer begins to decay.
Positrons ­ when tracers decay they emit positrons, which annihilate with electrons in brain producing gamma rays which are detected outside
body. Creating the image.
Laboratory experiments and the use of animals:
Animals are used a lot in research. Including Lesion studies ( where damage to the brain is caused and the change in behaviour is measured)
Causing damage to the brain would be the IV, and the resulting behaviour change is the DV.
comparing, behaviour of animals with brain damage to control group, make it possible to see which area of brain affect certain behaviour.…read more

Slide 4

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Evaluating laboratory experiments
Positives negatives
Validity If the IV and DV are naturally If the IV is manipulated then
occurring then the this is not very valid/ if the DV
experiment can be valid. can be interpreted differently
the = not valid.
Reliability Careful control of all EV, so Replication does not always =
replication and reliability can reliable, study findings can
be found. contradict themselves and
this can affect reliability
Generalizability If the sample is... random, If sample is... opportunity,
chosen to be representative, volunteer or biased then
or large enough then the finding cannot be generalised
results are generalizable. to target population.…read more

Slide 5

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Levels of measurement: METHODOLOGY PG4
There are three main levels of measurement.
1: = nominal, where categories are recorded e.g. yes/no ans. and whether you are male/female.
2: = ordinal data, which is ranked data where someone rates something on a scale.
3: = Interval/ratio data, which Is data where there is a real measurement such as height or time
Statistical test:
Mann-Whitney U test = used when a study is independent groups design and data is ordinal or ratio.
How to carry out a Mann Whitney test:
There are various steps involved in carrying out a Mann Whitney U test, The following outlines all 9 of them
1: Look at the number of participants in each group, and list them in separate columns
2: If one group is smaller than another, then rank the scores for both groups as one group. So take the lowest scores from the combined
group and place that at rank 1 and continue allocating ranks to higher values so rank 2,3,4 etc. Then separate the ranks into columns and
allocate them to the specific group they belong to.
3: Find then the total of the ranks for group A
4: Find the total of the ranks for Group B
(these step 5-9 are for Group A, repeat them for group B once the value for A is found)
5: Then multiply the number of participants from group A by that of group B.
6: Then add 1 to the number of participants in group A (NA) and multiply this value by the NA
7: Divide the answer for step 6 by 2.
8: Add the answers from step 5 and step 7.
9: subtract the answer from step 3 (Step 4 when doing it for B) from the answer from step 8
Then when the value for U is found for both A and B, you see which value is smaller from UA or UB and use this to see if the results are
significant or not using a statistical table.
Levels of significance:
Calculating the odds of something being due to chance…read more

Slide 6

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valuating the use of animals ­ Credibility, ethical and practical issues: METHODOLOGY PG5
1: animal unlikely to have prior knowledge that may affect their behaviour (like in humans) so findings = more valid + credible
1: what is being studied is often not the same as it would be for humans as the issue is often induced, e.g. Stress is induced on monkeys.
2: the genetic structure of animals are often not the same as humans so findings cannot always apply to humans = harder to generalise
1: procedures can be carried out that cannot in humans, giving an advanced knowledge to our brains and genetics
2: in drug development animals are necessary to test if drug is safe, the knowledge from this can improve humans lives
1: surgical procedures carried out, causes pain + discomfort for animals and some even die.
2: in lab experiments animals are confined in cages that do not represent their environment, some are even bred for experimentation.
3: as some results gathered from animals cannot be used in humans, so we have used the animals in vain as no advancements were made.c
Practical issues:
1: in genetic studies, animals can reproduce quickly and give birth quickly, so you can study more than one generation to view progress
2: some procedures require strict control of the environment which can be done with animals with caged environments,
1: animal not the same as humans, so can be difficult to generalise results, animals with similar brain structures are still not the same as us
2: in animal studies variables are isolated to study them, this is artificial and is not the same in real life as certain events can lead to others.…read more

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