MYP Maths Criterion B: Investigating Patterns — FAQ

Score well by working through all four strands: apply a clear mathematical strategy, describe patterns you notice, generalise them as a rule (usually algebraic), and justify or prove that generalisation. Top marks (7-8) need a correct, tested general rule with reasoning — not just a table of results and a guess.

Criterion B — Investigating Patterns — is one of four MYP Mathematics assessment criteria (alongside A: Knowing and Understanding, C: Communicating, D: Applying to Real-Life). It's marked out of 8, using descriptors from the IB's MYP Mathematics guide, and assesses your ability to select strategies, describe patterns, and form justified generalisations.

Criterion B is marked in four bands of 0-8: levels 1-2 (limited pattern selection), 3-4 (correct patterns described, basic strategy), 5-6 (patterns generalised, mostly correct), and 7-8 (correct general rule, justified or proved, applied to new situations). Each band has specific command terms — 'describe' versus 'justify' matters.

To generalise means turning a specific numerical pattern into an algebraic rule that works for any case, usually written with $n$ as the term number. Spotting that a sequence goes 3, 7, 11, 15 isn't enough — you need the rule $4n-1$ and evidence it works for terms you haven't tested.

Structure it in four clear stages: collect enough data to see a trend, describe the pattern in words, express it as an algebraic generalisation, then verify the rule using at least one case outside your original data. Skipping the verification step is the single most common reason students cap out at level 5-6.

Take a sequence of matchstick squares: 1 square uses 4 matches, 2 squares use 7, 3 squares use 10. The differences are constant at 3, so the rule is linear: $m=3n+1$. Testing $n=5$ gives $m=16$ — draw it out and count to confirm before calling it proven.

There's no fixed IB rule, but generalising from only 2-3 terms is a common mistake examiners flag — you can't tell a linear pattern from a quadratic one that early. Aim for at least 4-5 terms, and for quadratic or exponential patterns, check second differences or ratios before committing to a rule.

Describing means stating what you observe — 'the sequence increases by 3 each time.' Justifying means proving why your general rule works for all cases, often using algebra, a geometric argument, or induction-style reasoning. Level 7-8 responses always justify; level 3-4 responses usually only describe.

A correct final rule with no working, no tested verification, and no explanation of your strategy typically caps at level 3-4, regardless of accuracy — Criterion B marks the investigation process, not just the answer. Show your table, your reasoning for the rule, and one independent check to move into the higher bands.

Yes — a spreadsheet or graphic display calculator is fine for generating extra data points quickly, and doing so often strengthens your investigation by letting you test more cases. Just make sure you still explain your reasoning and generalisation in your own words; a table of numbers alone earns no marks for generalising.

Criterion B assesses investigating abstract or numerical patterns and generalising rules; Criterion D assesses applying mathematics to solve authentic real-world problems and evaluating the result's validity. A single task can combine both — investigate a pattern (B), then use the resulting model to answer a real-world question (D) — but they're graded separately.

The biggest lever is checking your child tests their generalised rule on a case they didn't use to find it — that single habit separates a level 5-6 from a level 7-8 in most MYP maths classes. Ask them to explain their pattern out loud before writing it algebraically; if they can't, the rule usually isn't secure yet.

MYP criteria don't feed directly into IB Diploma grades, but the skill Criterion B builds — spotting a pattern, generalising it algebraically, then proving it holds — is exactly what DP Maths AA (and AI, to a lesser extent) expects in Paper papers involving sequences, series, and proof by induction at Higher Level.