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examBoard: AQA
examType: GCSE
lessonTitle: Review and Practice - Correlation
Correlation is one of the most important research methods in psychology. It helps us understand how variables relate to each other without manipulating them directly. This makes it incredibly useful for studying real-world relationships that would be difficult or unethical to investigate experimentally.
Key Definitions:
Positive correlation: As one variable increases, the other also increases (e.g., study time and exam scores).
Negative correlation: As one variable increases, the other decreases (e.g., hours spent gaming and homework completion).
Zero correlation: No relationship exists between the variables (e.g., shoe size and intelligence).
Strong: Values close to +1 or -1 (e.g., 0.8 or -0.9)
Moderate: Values around +0.5 or -0.5
Weak: Values close to 0 (e.g., 0.2 or -0.1)
Remember: The closer to +1 or -1, the stronger the relationship!
Psychologists use several methods to visualise and calculate correlations between variables. Understanding these techniques helps you interpret research findings accurately.
A scatter diagram (or scatterplot) is a visual representation of the relationship between two variables. Each dot represents one participant's scores on both variables.
Dots form a pattern from bottom-left to top-right, showing that as one variable increases, so does the other.
Dots form a pattern from top-left to bottom-right, showing that as one variable increases, the other decreases.
Dots are scattered randomly with no clear pattern, showing no relationship between variables.
The most common way to calculate correlation is using Pearson's correlation coefficient (r). For your GCSE, you need to understand what the values mean rather than calculating them yourself.
r = +1.0: Perfect positive correlation
r = -1.0: Perfect negative correlation
r = 0: No correlation
r = +0.7: Strong positive correlation
r = -0.3: Weak negative correlation
One of the most important limitations of correlational research is that correlation does not imply causation. Just because two variables are related doesn't mean one causes the other.
Directionality problem: We can't tell which variable affects the other (if either does).
Third variable problem: An unseen third variable might be causing changes in both variables we're measuring.
Research shows a correlation between ice cream sales and drowning deaths. Does ice cream cause drowning? No! The third variable is hot weather, which increases both ice cream consumption and swimming (leading to more drowning accidents).
Correlational studies offer several benefits for psychological research:
However, correlational studies also have important limitations:
Researchers found a positive correlation (r = +0.65) between hours of sleep per night and academic performance in GCSE students. Students who slept 8-9 hours typically achieved higher grades than those who slept 5-6 hours.
However, this doesn't prove sleep causes better grades. Other explanations might include:
This illustrates why we must be careful when interpreting correlational findings.
Despite its limitations, correlational research is widely used in psychology for various purposes:
Correlational studies help identify factors associated with academic achievement, such as study habits, parental involvement and classroom environment.
Researchers use correlations to identify risk factors for mental health conditions and to evaluate the effectiveness of interventions.
Even though correlational studies don't manipulate variables, they still require ethical consideration:
To master correlation for your GCSE Psychology exam:
When answering questions about correlation in your exam:
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