GCSE MATHS • HIGHER TIER
Correlation Made Simple
Identify relationships between two variables, interpret scatter graphs and make sensible predictions.
Clear method
Exam practice
Worked proofs
Correlation in Four Moves
1
Identify
Look at the overall pattern of points or the relationship between the variables.
2
Describe
Decide whether the correlation is positive, negative or no correlation.
3
Interpret
Explain what the relationship means in the context of the variables.
4
Predict
Use a line of best fit for sensible estimates when the correlation is strong enough.
What You’ll Learn
Understand what correlation means.
Recognise positive, negative and no correlation.
Interpret patterns on scatter graphs.
Understand that correlation does not necessarily mean causation.
Use and interpret a line of best fit.
Use correlation to make predictions.
Key Rules
Correlation describes the relationship between two variables.
An upward trend shows positive correlation.
A downward trend shows negative correlation.
Randomly scattered points show no correlation.
Points closer together indicate a stronger correlation.
Describe the overall trend, not individual points.
Worked Proof: Correlation
Step-by-Step Method
- 1. Identify the two variables being compared.
- 2. Look at the overall pattern of the points.
- 3. Decide whether the correlation is positive, negative or absent.
- 4. Describe what the relationship means in context.
- 5. Draw a line of best fit through the middle of the points if required.
- 6. Use the line to make a sensible estimate.
- 7. Check whether the estimate lies within the data range.
More Worked Examples
1
Question : A scatter graph shows that as revision time increases, exam scores increase.
Answer : Positive correlation.
2
Question : A scatter graph shows that as speed increases, journey time decreases.
Answer : Negative correlation.
3
Question : A scatter graph shows no clear pattern between the variables.
Answer : No correlation.
4
Question : The points on a scatter graph rise from left to right.
Answer : Positive correlation.
- Common GCSE Mistakes
- Confusing positive and negative correlation.
- Assuming that correlation proves causation.
- Making predictions when there is little or no correlation.
- Describing individual points instead of the overall trend.
- Exam Tips
- Look at the overall direction of the scatter points.
- Upward trend means positive correlation.
- Downward trend means negative correlation.
- Randomly scattered points indicate no correlation.
- Do not claim that correlation automatically proves causation.
- Use a line of best fit only for sensible estimates supported by the data.
Skills Used in Correlation
Correlation
Scatter Graphs
Statistical Interpretation
Line of Best Fit
Interpolation
Data Handling
Predictions
Causation
Ready to Practise?
Printable Worksheet
Download and print practice questions with answers.
Interactive Quiz
Test your knowledge with instant feedback and hints.
Exam-Style Questions
Timed questions to build confidence for the real exam.
Watch the Correlation Tutorial
Step-by-step walkthroughs of Correlation with clear methods and exam tips.
Frequently Asked Questions
Correlation describes the relationship between two variables.
Positive correlation, negative correlation and no correlation.
As one variable increases, the other tends to increase as well.
As one variable increases, the other tends to decrease.
No. The source stresses that two variables can be related without one directly causing the other.
It shows the overall trend and can be used to estimate missing or unknown values.