Where IB Maths AI SL students lose marks — and exactly what to do about it
IB subject reports are released only to schools, so we have not read them and do not quote them. This page is built from the IB's free specimen markschemes, the IB's published syllabus hours, and public summaries by teachers and revision sites (each linked). Treat every point as lower confidence than our A Level and IGCSE pages, which use the boards' public reports.
Ordered by how often and how widely they were reported. The first 5 are free in full; Pro unlocks the fix and a worked example for every other one.
#1Accuracy: not exact, not 3 s.f., or rounded too early
What examiners saw: The public specimen markschemes state that answers should be exact or correct to 3 significant figures unless a question says otherwise. Tutor summaries of examiner feedback list rounding (and early rounding in multi-step questions) among the most common avoidable losses.
Fix: Keep full values in the GDC; round only the final answer, to 3 s.f. unless told otherwise. On Paper 1 (no calculator) leave answers exact.
Worked example (our own): A population grows as P = 1200e^(0.035t). Find t when P = 2000, then the population 5 years later.
Loses marks
e^(0.035t) = 5/3 ⇒ t ≈ 15
P(20) = 1200e^(0.7) = 2416.5, so 2420
Earns the marks
t = ln(5/3)/0.035 = 14.595… (keep this in the GDC)
Why: Rounding t to 15 before the second step changed the final answer. IB markschemes expect exact answers or 3 significant figures, from unrounded working.
What examiners saw: Revision-site guidance based on examiner feedback: method marks are given for writing what you asked the GDC to do. A bare wrong answer scores nothing.
Fix: Write the equation, function or distribution you entered, then the answer.
Worked example (our own): Solve x³ − 2x − 5 = 0.
Loses marks
x = 2.09
Earns the marks
x³ − 2x − 5 = 0 (solved on GDC)
x = 2.09 (3 s.f.)
Why: Write down the equation or function you entered. If the final value is wrong, the method mark depends on it.
What examiners saw: Revision-site guides call the sign convention the most common cause of cascading errors in financial questions: PV and PMT with the same sign, FV not zero, P/Y and C/Y not set.
Fix: Money received positive, money paid negative. Set P/Y and C/Y, and write all the values you entered.
Worked example (our own): A $10 000 loan at 5% annual interest, compounded monthly, is repaid monthly over 5 years. Find the monthly payment.
#4Chi-squared tests: degrees of freedom, small expected values, conclusions
What examiners saw: Revision guides highlight df errors, not combining categories with expected frequencies below 5, and conclusions that are not in context.
Fix: df = (r − 1)(c − 1) for independence; combine cells if any expected frequency < 5; conclude in the words of the question.
Worked example (our own): A 3 × 2 contingency table is used to test whether preference depends on age. The p-value is 0.031. State the degrees of freedom and a conclusion at the 5% level.
Loses marks
df = 6 − 1 = 5. p < 0.05 so reject H₀.
Earns the marks
df = (3 − 1)(2 − 1) = 2
p = 0.031 < 0.05, so reject H₀
There is evidence at the 5% level that preference depends on age
Why: df = (rows − 1)(columns − 1). A conclusion must be in context; if any expected frequency is below 5, combine rows or columns first.
#5Probability: calculator syntax instead of notation, and "at least" misread
What examiners saw: Secondary guidance: examiners expect the distribution and probability statement, not GDC syntax, and "at least" is often translated wrongly.
Fix: Write X ~ B(n, p) and the probability statement (e.g. 1 − P(X ≤ 3)), then the value.
Worked example (our own): X ~ B(10, 0.3). Find P(X ≥ 4).
Loses marks
binomcdf(10, 0.3, 4) = 0.850
Earns the marks
P(X ≥ 4) = 1 − P(X ≤ 3)
= 1 − 0.6496… = 0.350 (3 s.f.)
Why: Write the distribution and the probability statement in mathematical notation, not calculator syntax, and translate "at least" carefully.
What examiners saw: Secondary summaries of subject-report feedback single out trigonometry done with the GDC in the wrong mode, spoiling every later part of a question.
Pro: the fix and a worked example (wrong vs right method) for this mistake are in Pro. See plans
The IB does not publish marks per topic and we have no question-level data for IB papers. Syllabus hours are a rough guide to how much of the exam each topic takes up. Total: 120 hours.
A one-page PDF of the ten most common mark-losing mistakes and how to avoid them. Print it and stick it inside your revision folder.
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Sources
Where this comes from
IB subject reports are released only to schools, so we have not read them and do not quote them. This page is built from the IB's free specimen markschemes, the IB's published syllabus hours, and public summaries by teachers and revision sites (each linked). Treat every point as lower confidence than our A Level and IGCSE pages, which use the boards' public reports.
IB subject reports (DP Mathematics AA and AI) — not used (restricted). The IB publishes a subject report after each session, but it is only available to schools. We did not use leaked copies. Everything on this page comes from public sources.
What are the most common mistakes in IB Maths AI SL?
The most repeated points are: Accuracy; GDC answers with no working written down; Finance. Each one on this page has the fix and, where free, a worked example showing the wrong and right method.
Which IB Maths AI SL topics come up most?
In the material we analysed, the biggest areas were Statistics and probability (36 hours), Functions (31 hours), Calculus (19 hours).
Is this a prediction of the May 2027 paper?
No one outside the exam board knows what will be on the next paper. The "focus" list is an informed prediction from how often topics appeared and how weakly they were answered; it is not a guarantee, so revise the whole specification.
Where does this information come from?
IB subject reports are released only to schools, so we have not read them and do not quote them. This page is built from the IB's free specimen markschemes, the IB's published syllabus hours, and public summaries by teachers and revision sites (each linked). Treat every point as lower confidence than our A Level and IGCSE pages, which use the boards' public reports.
IB Math Revision