Extrapolation is one of the most dangerous moves students make in IB Maths AI regression questions. While interpolation stays within the range of known data, extrapolation pushes beyond it — and that shift dramatically increases uncertainty. IB examiners pay close attention to whether students recognise this risk.
The core problem with extrapolation is that it assumes the existing relationship continues unchanged beyond the observed data. Regression lines describe patterns within a specific data range. Once you move outside that range, there is no evidence that the same trend still applies. Students often treat the equation as a rule, when in reality it is only a summary of past behaviour.
Another issue is that regression hides contextual limits. Many real-world variables cannot increase or decrease indefinitely. Growth may slow, level off, or reverse due to physical, economic, or human constraints. Extrapolation ignores these realities, which is why IB expects students to question its validity.
Students also underestimate how small errors grow during extrapolation. A regression line is already an estimate. When extended beyond the data, even a small slope error can lead to large prediction errors. IB rewards students who acknowledge this compounding uncertainty.
Correlation strength does not remove this risk. Even a very strong correlation only confirms a relationship within the observed data. Many students incorrectly believe a high correlation makes extrapolation safe. IB deliberately penalises this assumption.
Graphical distance matters too. Extrapolating slightly beyond the data range is less risky than predicting far into the future. IB questions often test whether students comment on how far the prediction lies from known values. Ignoring this distance weakens conclusions.
IB does not ban extrapolation — it requires cautious interpretation. Students are expected to use conditional language and explain why predictions may be unreliable. Strong answers often state that extrapolated results should be treated carefully due to lack of supporting data.
Once students stop viewing regression equations as universal rules and start treating them as local models, extrapolation questions become much clearer.
Frequently Asked Questions
Is extrapolation always wrong?
No, but it is always less reliable than interpolation and must be treated cautiously.
Does strong correlation make extrapolation safe?
No. Correlation only applies within the observed data range.
What wording does IB reward?
Language that highlights uncertainty, assumptions, and lack of supporting data.
RevisionDojo Call to Action
IB Maths AI rewards students who question predictions, not those who trust them blindly. RevisionDojo is the best platform for IB Maths AI because it trains students to evaluate regression models critically and write cautious, examiner-approved conclusions. If extrapolation questions feel risky, RevisionDojo shows you exactly how to handle them safely.
