Maths IA criteria · 3 marks
Criterion C: Personal engagement
Personal engagement is the most misunderstood criterion. It is not about how hard you worked or how much you love the topic. It is about evidence, throughout the exploration, that you made the mathematics your own. It is worth 3 marks.
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What Criterion C assesses
The extent to which you engage with the exploration and make it your own — independent thinking, creativity, and a personal approach to the mathematics — shown in the work itself, not claimed in the introduction.
This is our summary, not the IB's wording. The descriptors themselves, with a checklist and a self-grade sheet, are on the IA criteria page. For a rough band for your own draft, answer the guided questions in the free IA self-check.
What the mark bands look like in practice
| Band | What the examiner typically sees |
|---|---|
| Low (1) | Engagement is limited or superficial: a personal reason in the introduction, then a standard textbook-style exploration. |
| Middle (2) | Some genuine engagement: the student makes some of their own choices, but much of the work follows a well-known path. |
| Top (3) | Significant engagement that drives the exploration: the student's own questions, predictions, data and decisions shape what happens next, on many occasions. |
Our summary in plain English, not IB wording — see the official IB guide via your teacher.
Checklist for Criterion C
- Your own question — not a topic lifted from a list without changes.
- Predictions made before calculating, then tested (“I expected the exponential to fit better because…”).
- Questions you ask and answer along the way (“Would this still work for a deeper chain?”).
- Your own data or measurements where possible, and your own decisions about how to collect them.
- Decisions explained: why this model, why this method, why not the obvious alternative.
- Mathematics that is unfamiliar to you, clearly explained in your own words (and said to be new to you).
- Different perspectives: comparing methods, historical or global context used mathematically.
- Your own presentation of the results — your graphs, your tables, your explanations.
Examiner tips
Show, don't tell.
“I have always loved football” earns nothing on its own. Choosing to test your own penalty data, predicting the result, and explaining why your prediction was wrong is personal engagement.
Avoid the textbook route.
If your exploration could be a worked example in a textbook, it will struggle here. Change the question, the data or the method until it is recognisably yours.
Engagement is not effort.
Examiners mark the evidence on the page. Twenty hours of work that reads like a report of a standard method can still score low; a modest exploration full of your own decisions can score full marks.
Weak vs strong: an example
Loses marks
“I chose this topic because I am interested in basketball. Next, I will calculate the correlation coefficient.”
Earns marks
“Before calculating r, I predicted a weak correlation, because in my own team the tallest player is not our best shooter. The value r ≈ 0.12 supports this, but it made me wonder whether distance from the basket is the real variable — so I recorded where each shot was taken from.”
Common Criterion C mistakes
- Personal engagement only in the first paragraph.
- Choosing a topic from a list and following a published approach step by step.
- Reporting what you did without ever explaining why.
- Using data from a single website with no decisions about how to clean or select it.
What the IB subject reports say about Criterion C
- Saying you are interested, telling a personal story or collecting your own data is not enough on its own: the reports look for independent decisions inside the mathematics.
- Templates (a common one is a Voronoi diagram followed by a travelling-salesman route) and research-style reports leave almost no room for engagement.
- Small but meaningful changes to a familiar problem, predictions you test, and mathematics you adapt when a difficulty comes up are what earn the higher levels.
- Adding extra models or tests without a reason is not “exploring from different perspectives”.
Our own summary of the moderators' comments in the IB's Mathematics subject reports (AA and AI, SL and HL, May 2024 to November 2025), which the IB releases to schools. Not the IB's wording, and not an IB publication.
Frequently asked questions
Does personal engagement mean writing about myself?
No. A personal reason for choosing the topic is fine, but the marks come from evidence of your own thinking throughout the mathematics: predictions, questions, decisions and your own approach.
Can a pure maths IA score well on personal engagement?
Yes. Exploring small cases yourself, making conjectures, trying approaches that fail and explaining what you learned is strong personal engagement even with no real-world context.
Does collecting my own data guarantee full marks for C?
No — it helps, but what matters is what you do with it: the decisions you make, the questions you ask, and how the data shapes your exploration.
Personal engagement when you model data
Choosing the model from your own context — and saying why before you fit it — is personal engagement: the period of a tide, the ceiling of a population, the asymptote of a cooling curve. The sinusoidal and logistic examples show those decisions step by step, and Model my data lets you try them with your own numbers.
Related: all five criteria with a self-grade sheet · annotated exemplars marked on every criterion · have Pete review your draft one-to-one · IA structure and format
Types of IA where the data or the decision is yours from the start: survey-based investigations · voting, fairness & game theory · trigonometry, navigation & surveying.
Free: the Criterion C checks, and the other four, in one PDF
The checklist Pete uses with his own students: every check for Criteria A–E (including the Criterion C list above) in a 4-page PDF, the mistakes that cost the most marks, and a self-assessment grid. We'll email it to you, and for three weeks your weekly email carries one IA tip, timed to your deadline if you give it. Free — no account, no payment.
While you wait for the email: see Criterion C at the top band in a free annotated excerpt →