Scatter graphs and correlation
Plot bivariate data; describe correlation (positive, negative, none); draw a line of best fit.
GCSE expects you to plot, identify correlation type and strength, draw a line of best fit by eye (going through the centroid), and use it to predict (interpolate within the range; extrapolation is risky).
Worked examples
Hours studied vs exam score: positive correlation.
Outside temperature vs heating bill: negative correlation.
Line of best fit predicts y from x within the data range.
Frequently asked questions
Correlation = causation?
No. Correlation tells you variables vary together; it doesn't prove one causes the other.
Extrapolation?
Predicting outside the data range. Unreliable — relationships may not hold beyond the observed values.