A-level maths / Applied Year 1

Correlation

Investigate how two variables vary together and judge what a fitted model can tell you.

Start with the available lessons below. Correlation, regression and independent practice are being added in chapter order.

Scatter diagrams and paired dataKeep paired observations together, choose explanatory and response axes, plot labelled scatter diagrams and handle repeated or missing pairs honestly.
Describing correlationDescribe direction, strength and shape of association; distinguish correlation strength from gradient and recognise curved patterns and influential observations.
Correlation and causationDistinguish association from causal effects, investigate confounding and reverse direction, and explain how random allocation and representative sampling answer different questions.
Least squares and residualsCalculate signed vertical residuals, compare sums of squared residuals and understand what a y-on-x least-squares fit minimises, including outlier influence and model limits.
Interpreting regression linesInterpret regression gradients and intercepts with units, distinguish predicted levels from changes and transform fitted equations when units or reference values change.
Regression predictions and reliabilityCalculate fitted predictions, classify interpolation using the explanatory-variable range and judge extrapolation, scatter, sample context and model limitations.
Choosing the regression directionChoose y-on-x or x-on-y regression, distinguish rearranging a given equation from fitting the reverse prediction and understand the perfect-line exception.