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Correlations
A correlation is a relationship between two variables where changes in one variable go along with changes in the other variable.
Two Basic Kinds of Correlations:
Positive: the variables change in the same direction, like more friends and more happiness.
Negative: the variables change in opposite directions, as class absences increase, grades tend to decrease.
The Coefficient of Correlation
The coefficient is the number used to express the strength of the connection, including the plus or minus sign.
A correlation is a relationship between two variables where changes in one variable go along with changes in the other variable.
Two Basic Kinds of Correlations:
Positive: the variables change in the same direction, like more friends and more happiness.
Negative: the variables change in opposite directions, as class absences increase, grades tend to decrease.
The Coefficient of Correlation
The coefficient is the number used to express the strength of the connection, including the plus or minus sign.
- A value of 0.00 means there is no relationship between the variables.
- A value of +1.00 means a perfect, positive correlation.
- Weaker positive correlations have values higher than .00 but lower than +1.00.
- A value of -1.00 means a perfect, negative correlation.
- Weaker negative correlations have values higher than –1.00 but lower than 0.00.
Correlation Coefficients
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A correlation checks to see if two sets of numbers are related; in other words, are the two sets of numbers corresponding in some way.
In the case of psychology, the numbers being analysed relate to behaviours (or variables that could affect behaviour) but actually any two variables producing quantitative data could be checked to establish whether a correlations exists. Each of the two sets of numbers represents a co-variable. Once data has been collected for each of the co-variables, it can be plotted in a scattergram and/ or statistically analysed to produce a correlation coefficient. Scattergrams and coefficients indicate the strength of a relationship between two variables, which highlights the extent to which two variables correspond. The relationship between two variables will always produce a coefficient of between 1 and -1. Coefficients with a minus in front of them highlight a negative correlation which means that as one set of numbers is increasing the other set is decreasing or as one decreases the other increases, so the trend in the data from one variable opposes the other. Coefficients which are positive indicate that both sets of data are showing the same trend, so as one set of data increases so does the other or as one set decreases the same trends is observed in the second set of data |
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Strengths and Weaknesses of Correlational Analyses
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Strengths
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Examples of Practical Work: Correlations
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Some Key Terms
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Correlations: a statistical technique used to calculate the correlation coefficient in order to quantify the strength of relationship between two variables.
Ethical guidelines: the British Psychological Society (BPS) has issued a set of ethical guidelines for research involving human participants. These ethical guidelines are designed to protect the well-being and dignity of research participants.
External (ecological) validity: the validity of a study outside the research situation and the extent to which the findings can be generalised.
Internal (experimental) validity: the extent to which a measurement technique measures what it is supposed to measure, whether the IV really caused the effect on the DV or whether some other factor was responsible.
Operationalisation of variables: being able to define variables in order to manipulate the IV and measure the DV, e.g. performance on a memory test might be operationalised as ‘the number of words remembered from a list of words’.
Quantitative data: objective, precise, usually numerical, data that can be statistically analysed.
Reliability: reliability of results means consistency. In other words, if something is measured more than once, the same effect should result.
Volunteer sampling: self selected participants volunteer to participate, e.g. by responding to advertisements.
Ethical guidelines: the British Psychological Society (BPS) has issued a set of ethical guidelines for research involving human participants. These ethical guidelines are designed to protect the well-being and dignity of research participants.
External (ecological) validity: the validity of a study outside the research situation and the extent to which the findings can be generalised.
Internal (experimental) validity: the extent to which a measurement technique measures what it is supposed to measure, whether the IV really caused the effect on the DV or whether some other factor was responsible.
Operationalisation of variables: being able to define variables in order to manipulate the IV and measure the DV, e.g. performance on a memory test might be operationalised as ‘the number of words remembered from a list of words’.
Quantitative data: objective, precise, usually numerical, data that can be statistically analysed.
Reliability: reliability of results means consistency. In other words, if something is measured more than once, the same effect should result.
Volunteer sampling: self selected participants volunteer to participate, e.g. by responding to advertisements.
Prep Model Answers
A psychologist was interested in the relationship between individuals’ language ability and their physical co-ordination. She used a correlational analysis to investigate this in a self-selected sample of 34 adult participants. Each participant completed a language ability test. This test involved both having to spell a list of 20 words and answering 20 closed questions on the meaning of words. The participants’ physical co-ordination was then calculated by rating them on six different tasks including balancing on a beam, catching a ball and copying a dance routine.
1. The psychologist’s hypothesis predicted a significant negative correlation. Using this information above, explain what she was expecting the results to show. [2]
2. Write a closed question which could have been used to test participants’ understanding of the meaning of a word. [1]
What does the word ‘validity’ mean?
A. Truthfulness
B. Consistency
3a. Explain why the data collected in this study is an example of quantitative data. [3]
Quantitative data is data in numbers / quantities. This is data in numerical form because they had to spell a list of 20 words, so the answers would be right or wrong, giving them an overall score out of 20.
3b. Name the graph that would be used to show a correlational analysis. [1]
Scattergraph
3c. Name the section of a practical report where a graph would be presented. [1]
Results
4. Explain one strength and one weakness of using a self-selected sample in this study. [6]
A strength of using a self-selected sample in this study is that it is easy to be ethical, as participants have already given their consent to take part. This is important in this study as participant are going to have to do spelling tests and physical tasks including balancing on a beam, catching a ball and copying a dance routine, which some people might not want to consent to.
A weakness of using a self-selected sample in this study as there could be a sample bias and the sample will be biased because of the type of person who volunteer for research, rather than representing the target population. This is a problem in this study as the people who choose to take part may be better at physical tasks like balancing on a beam, catching a ball and copying a dance routine than other people.
5. Outline how each of the following ethical considerations could have been dealt with in this study.
a. Confidentiality [2]
No one outside of the experiment should be able to identify the participants from their results of their scores on spellings and how they were rated in terms of physical co-ordination. The psychologist could use their initials or a code rather than their names.
b. Informed consent [2]
The psychologist should gain consent from the participants before they do any testing and make sure they know that the tests are to see whether people who can spell better have poor co-ordination skills.
c. Protection of participant [2]
The psychologist should make sure that she does her upmost to prevent any undue stress for her participants, especially when giving them their scores on spellings and how they were rated in terms of physical co-ordination.
A psychologist was interested in the relationship between individuals’ language ability and their physical co-ordination. She used a correlational analysis to investigate this in a self-selected sample of 34 adult participants. Each participant completed a language ability test. This test involved both having to spell a list of 20 words and answering 20 closed questions on the meaning of words. The participants’ physical co-ordination was then calculated by rating them on six different tasks including balancing on a beam, catching a ball and copying a dance routine.
1. The psychologist’s hypothesis predicted a significant negative correlation. Using this information above, explain what she was expecting the results to show. [2]
- Negative correlation – as one co-variable increases (e.g. language ability) the other co-variable decreases (e.g. physical co-ordination).
- The better the person’s language skills, the worse the person’s physical co-ordination will be.
2. Write a closed question which could have been used to test participants’ understanding of the meaning of a word. [1]
What does the word ‘validity’ mean?
A. Truthfulness
B. Consistency
3a. Explain why the data collected in this study is an example of quantitative data. [3]
Quantitative data is data in numbers / quantities. This is data in numerical form because they had to spell a list of 20 words, so the answers would be right or wrong, giving them an overall score out of 20.
3b. Name the graph that would be used to show a correlational analysis. [1]
Scattergraph
3c. Name the section of a practical report where a graph would be presented. [1]
Results
4. Explain one strength and one weakness of using a self-selected sample in this study. [6]
A strength of using a self-selected sample in this study is that it is easy to be ethical, as participants have already given their consent to take part. This is important in this study as participant are going to have to do spelling tests and physical tasks including balancing on a beam, catching a ball and copying a dance routine, which some people might not want to consent to.
A weakness of using a self-selected sample in this study as there could be a sample bias and the sample will be biased because of the type of person who volunteer for research, rather than representing the target population. This is a problem in this study as the people who choose to take part may be better at physical tasks like balancing on a beam, catching a ball and copying a dance routine than other people.
5. Outline how each of the following ethical considerations could have been dealt with in this study.
a. Confidentiality [2]
No one outside of the experiment should be able to identify the participants from their results of their scores on spellings and how they were rated in terms of physical co-ordination. The psychologist could use their initials or a code rather than their names.
b. Informed consent [2]
The psychologist should gain consent from the participants before they do any testing and make sure they know that the tests are to see whether people who can spell better have poor co-ordination skills.
c. Protection of participant [2]
The psychologist should make sure that she does her upmost to prevent any undue stress for her participants, especially when giving them their scores on spellings and how they were rated in terms of physical co-ordination.
