Maths IA guide

Maths IA mistakes that cost marks

Most IAs do not lose marks because the mathematics is too easy. They lose marks through small, fixable problems that appear again and again. These are the ones Pete Bromfield flags most often with his students — grouped by criterion, each with the fix.

Guidance based on the checklist Pete Bromfield — a practising IB Mathematics Internal Assessment examiner and former Head of Maths — uses with his own students. Not affiliated with or endorsed by the IB.

Criterion A: Presentation

  1. No clear aim. Fix: State a precise question in one or two sentences near the start, and answer it in the conclusion.
  2. Writing for the teacher, not a peer. Fix: Explain every step so a classmate who has not studied your topic could follow.
  3. Repeated calculations. Fix: Show one worked example, then a table of results.
  4. Graphs in the wrong place. Fix: Put each graph next to the paragraph that discusses it; move raw data, not analysis, to the appendix.
  5. Tables split across pages without headings. Fix: Repeat the column headings on the new page, or keep the table together.
  6. Padding. Fix: Cut history, biography and definitions that do not serve the aim.

Full guide to Criterion A

Criterion B: Mathematical communication

  1. Calculator notation. Fix: Write x², e^(kt) as a proper exponent and ×, never ^, * or E.
  2. Undefined variables. Fix: Define each variable, with units and domain, the first time it appears.
  3. Unlabelled graphs. Fix: Title, axis labels, units and scales on every graph; show axis breaks.
  4. = for rounded values. Fix: Use ≈ and state your rounding rule once, with a reason.
  5. Inconsistent notation. Fix: Use an equation editor and keep the same symbols throughout.
  6. Statistics you never use. Fix: Only calculate a standard deviation, IQR or r² if you interpret it.

Full guide to Criterion B

Criterion C: Personal engagement

  1. Engagement only in the introduction. Fix: Add predictions, questions and decisions throughout the mathematics.
  2. A textbook exploration. Fix: Change the question, data or method until it is recognisably yours.
  3. No explanation of choices. Fix: Say why you chose each method or model, and why not the alternative.

Full guide to Criterion C

Criterion D: Reflection

  1. Reflection only at the end. Fix: Add a short reflection after each major result.
  2. Generic limitations (“human error”). Fix: Name the limitation that most affects your answer and estimate its effect.
  3. Describing instead of interpreting. Fix: Say what each result means in context and whether it is reasonable.
  4. Reflection that changes nothing. Fix: Let reflection lead to the next step: a better model, a new test, a refined question.

Full guide to Criterion D

Criterion E: Use of mathematics

  1. Line of best fit without r. Fix: Calculate and interpret the correlation, and justify a linear model, before drawing any line.
  2. Answers without working. Fix: Show reasoning and explain technology output; a correct answer alone scores very little.
  3. Test conditions ignored. Fix: Check sample size, expected frequencies ≥ 5, independence and distribution assumptions.
  4. Maths below the course level. Fix: Include techniques from your course that genuinely help answer the aim.
  5. Copied advanced maths. Fix: Only use mathematics you can explain in your own words; say when it is new to you.
  6. Untested models. Fix: Test models with residuals or on data you did not use to build them.

Full guide to Criterion E

Frequently asked questions

What is the most common Maths IA mistake?

In Pete Bromfield's experience of marking, the most common is drawing a line of best fit on a scatter graph without first calculating the correlation and justifying why a linear model is appropriate.

Can small presentation mistakes really lower my grade?

Yes. Criteria A and B together are worth 8 of the 20 marks, and they are mostly lost through fixable issues: a vague aim, repeated calculations, calculator notation and unlabelled graphs.

Tools for every stage of your IA

IA plannerAnswer the planning questions, save them and share with your teacher. Desmos workspacePlot your data, fit models and keep your graphs with your plan. AI feedback on a draftCriterion-by-criterion feedback with evidence from your own text. Coaching, not rewriting. Examiner reviewPete, a practising IA examiner, reads your draft and talks it through with you (€100).