IB Mathematics Internal Assessment
Criterion B is about whether a reader can follow your mathematics without having to guess. The mathematics can be sound and still lose marks here. These are the mistakes I see most often, and what to do about each one.
Put simply: can someone who has studied the same course, but has never met your topic, read your exploration and follow the mathematical argument from start to finish? That is the test. It is not about beautiful formatting, and it is not about length. It is about whether the mathematics is set out so that it can be read.
Because it is judged across the whole document, communication is rarely lost in one dramatic place. It leaks away a little on every page. That is why it pays to check for these mistakes deliberately.
Writing 2^3 instead of 2 cubed, or 5E-3 instead of 5 × 10 to the power of minus 3, or typing a function as "y=x^2*sin(x)". This is the single most common slip. Software notation belongs in your working notes, not in the finished page.
Use proper mathematical notation everywhere. If your word processor makes that painful, learn its equation editor once, early, rather than fighting it the night before the deadline.
A formula appears with several letters in it and the reader is left to work out which is a rate, which is a time and which is a constant you invented. Even standard symbols can mean different things in different places.
Define each variable the first time it appears, with its meaning and its units. Keep the same symbol for the same quantity throughout. If you change a symbol halfway through, you have created a reading problem.
A screenshot of a regression table, a spreadsheet block or a graphing window, dropped in with one line under it. The reader sees output but cannot tell what you asked for, what it means or why you trust it.
Say what you did and why, then present the result in your own words and notation, and say what it tells you. A screenshot can sit alongside that, but it cannot replace it.
No axis labels, no units, no title, a scale that hides the pattern, or a table with columns nobody has named. The reader has to hunt through the text to decode it.
Every graph and table should make sense on its own: labelled axes with units, a caption, a sensible scale. Then refer to it by number in the text, so the reader knows why it is there.
Line one, then a result three lines later, with the middle missing. It may be obvious to you, because you did the work. The reader was not there.
Show the key steps, and connect them with a short phrase saying what you are doing and why. You do not need to show trivial arithmetic. You do need to show anything a peer would have to stop and think about.
Answers quoted to ten decimal places straight from a calculator, or three significant figures in one place and six in the next. It signals that nothing was decided, and it makes tables hard to read.
Decide on a level of precision that matches the precision of your data, use it consistently, and say so once. Precision you cannot justify is noise.
Pages of background, repeated definitions, or the same working shown for five near-identical cases. The mathematics you want the reader to see gets buried, and the whole thing becomes harder to follow.
Show one worked case in full, then summarise the rest in a table. Move anything the argument does not depend on into a short appendix, or cut it.
One long stream of text with no clear aim near the start, no sections, and no sense of where the exploration is heading. The reader cannot tell what the point of a paragraph is until much later, if ever.
State your aim early, use clear section headings, and open each section with a sentence saying what it will establish. Finish by returning to the aim. Structure is not decoration; it is how a reader keeps their place.
A figure or dataset that appears from nowhere, or a formula used without saying where it came from. The reader cannot tell what is yours and what is borrowed.
Say where data came from and how it was collected, and reference anything you have relied on, in a consistent style. Being clear about what is yours also helps your case on personal engagement.
Give your draft to a friend who takes the same course but knows nothing about your topic. Ask them to read one section and tell you, in their own words, what you did and why. Do not help them. Wherever they stall, mark the spot.
Almost every stall traces back to one of the nine mistakes above: an undefined symbol, a missing step, a graph they could not read. Fixing those spots is worth more than another round of polishing the parts that already work.
AA and AI are judged against the same five criteria, and communication reads the same way in both. What changes is the mathematics you are communicating. At HL, where the mathematics is often more involved, clear notation and well-chosen steps matter even more, because there is more for the reader to lose track of. At SL, the risk is more often thin explanation of methods that feel simple to you.
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Written by a serving IB Diploma and Career-related Programme Coordinator and Head of Mathematics, who reads internal assessments across every subject group every year. If you then want the whole draft reviewed properly against all five criteria, that is the paid one, and it is refunded if it does not name at least three specific things to fix.
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I never write any part of it. Not a sentence, not a calculation, not your data. Under 18: a parent buys this and the thread is with them. I do not work with students at my own school.