GCSE-ready- Home
- Lessons
- GCSE & IGCSE Mathematics
- Scatter graphs and correlation
Scatter graphs and correlation
Scatter graphs show whether two variables are related, and let you make predictions.
Correlation
Positive: as one goes up, the other goes up.
Negative: as one goes up, the other goes down.
No correlation: no clear pattern.
Correlation does not prove one thing causes the other.
Negative: as one goes up, the other goes down.
No correlation: no clear pattern.
Correlation does not prove one thing causes the other.
Line of best fit
Draw a straight line through the middle of the points, with roughly equal numbers on each side. Use it to estimate values.
Interpolation and extrapolation
Interpolation: estimating within the range of the data, which is fairly reliable.
Extrapolation: estimating outside the range, which is unreliable.
An outlier is a point far from the pattern.
Extrapolation: estimating outside the range, which is unreliable.
An outlier is a point far from the pattern.
A line of best fit gives y = 2x + 10 for revision hours (x) and test score (y). Estimate the score for 15 hours.
- y = 2 × 15 + 10
Answer: 40
Positive, negative or no correlation. A line of best fit follows the trend. Interpolation is reliable; extrapolation is not. Correlation is not causation.
Check you have got it
Answer 6 quick questions with instant marking. If you get one wrong, GCSE-ready shows you why and gives you another go. It is free, and you do not need an account.