Research methods 9.1.8 - additional research methods and techniques Flashcards
what is a correlational study?
a way of establishing whether there is a relationship between two variables
how should a correlational study be conducted?
- measure the two variables to obtain a set of paired scores
- analyse the relationship by drawing a scatterplot or calculating a correlation coefficient
what does a correlation coefficient do?
tell you the strength and direction of the correlation
how should the value of a correlation coefficient be interpreted?
positive number = positive correlation
negative number = negative correlation
the closer the number to 0, the weaker the correlation (+1 and -1 are the strongest possible correlations)
how can a correlation be used?
if you know someone’s score on one variable and there is a correlation between the variables, you can predict their score on the other variable
what does the accuracy of the prediction depend on?
how strong the correlation is - the stronger the correlation, the more accurate the prediction
how do you calculate correlation coefficient using Spearman’s rank?
- rank the data (separate rank for data in each variable) - lowest gets a rank of 1 and so on
- find the difference (D) between the ranks for the corresponding data for each variable
- square D to get D^2
- add up all the D^2s to get 𝚺d^2
- find n (total number of pairs of data)
- substitute the values into the equation to find R (remember to include +/- in final answer)
when ranking data, what do you do if you have tied scores?
use up the same number of ranks as there are tied scores, but give all the tied scores the same rank which is the number in the middle of the ranks being used up
what are the problems with interpreting a correlation?
the correlation doesn’t tell you which variable is influencing the other
it may be hard to find an explanation for the correlation which could lead to inaccurate assumptions (eg. there may be another variable which isn’t mentioned)
what is the key rule to remember about correlation?
correlation does not equal causation (for all correlations, there are at least three possible interpretations)
twin studies - what are monozygotic twins?
identical twins which share 100% of the same genetic material
twin studies - what are dizygotic twins?
fraternal twins which share 50% of the same genetic material
twin studies - how are they conducted?
psychologists compare behaviour between groups of monozygotic and dizygotic twins to see which group share the most similarity between each set of twins
twin studies - what is the concordance rate?
the extent to which behaviour is the same between twins
twin studies - how are the results of them interpreted?
if the concordance rate is higher in monozygotic than dizygotic twins, psychologists conclude there may be a genetic element influencing that behaviour
if the concordance rates are similar between both types of twins, researchers will infer there isn’t a significant genetic component affecting the behaviour - it may be due to experiential factors as twins usually have similar upbringings
this is because the greater similarity of the MZ twins can only be explained by their greater genetic similarity
twin studies - what does it mean if the correlation for monozygotic twins is less than 1?
the characteristic is not just due to genes - environmental factors influence it too
twin studies - what are weaknesses?
difficult to distinguish nature from nurture - most twins are raised together, so even if mz twins show higher concordance rate than dz twins, can be problematic to assume this is due to genetic factors
difficult to recruit large and diverse samples of mz and dz twins, so it may be hard to generalise results of studies
rely on fact that MZ and DZ pairs have identical environments but this may not be true as MZ pairs may be treated more similarly than DZ pairs as they are the same gender while DZ pairs may not be
what is the strength of twin studies over adoption studies?
you can use the correlation values to work out the size of the genetic or environmental influence
eg. correlation for MZ twins is 0.35
0.35^2=0.123=12.3%, therefore the trait is influenced by genetics in 12.3% of twins
adoption studies - how are they conducted?
adoptees are studied and their behaviour is correlated with their adopted and biological families
psychologists can then infer whether a behaviour is due to nature of nurture, because adoptees share an environment with their adopted family but genetic material with their biological family
adoption studies - how are the results of studies interpreted?
if the adoptees’ behaviour is more similar to that of their adoptive family, you can conclude that the behaviour is likely due to the shared environment
if the behaviour correlates more strongly with that of their biological family, it is likely to be caused by a biological component
adoption studies - what are weaknesses?
rely on children being adopted immediately after birth - if they aren’t there will be confounding variables where biological parents or foster care has contributed some of the environment, not jut adopted parents
adopted children are often put with families which reflect the family background they came from - adoptee and biological family may have had similar experiences even if they weren’t together, so it is unreliable to assume the similarities are due to genetics
rare to obtain data from all parents particularly biological ones
what is the strength of twin and adoption studies?
they allow us to separate out genetic and environmental influences and see which has a greater effect on behaviour
