RevisionPrep FAQ
How Do You Write a Strong MYP Maths Investigation (Criterion B)?
Answered by RevisionPrep's IB Educators
A strong MYP Maths investigation for Criterion B moves from a clear pattern, through a tested rule, to a justified generalisation — usually algebraic — with reasoning for why it works, not just that it works. Below, we unpack exactly how examiners read this criterion, level by level.
Understanding Criterion B
How do you write a strong MYP Maths investigation (criterion b)?
A strong Criterion B investigation states a clear pattern from your data, tests it against new cases, then generalises it algebraically with working shown. According to the MYP: From Principles into Practice guide, Criterion B (Investigating Patterns) is assessed 0–8, and top marks need a generalisation described, tested AND justified — not just spotted.
Here's the sequence I drill into every student:
- Collect enough data (at least 4–5 cases) before guessing a rule.
- Describe the pattern in words first — this proves you actually see it.
- Write the rule algebraically (e.g. ).
- Test it on a case you haven't used yet.
- Justify why it works — link back to the structure of the problem, not just the numbers. Miss step 5 and you cap out around a level 5–6, even with correct algebra.
What does 'justifying a generalisation' actually mean in criterion b?
Justifying means explaining why your rule must be true for every case, using the structure of the problem — not just showing it works for the numbers you tried. Think proof, not pattern-spotting: relate the algebra back to what's physically happening in the diagram, sequence or table.
Quick tip: examiners often reward a short verbal explanation ('each new layer adds 4 dots because a square has 4 sides') more than extra algebra with no reasoning attached. If you can't explain your rule out loud in one sentence, it isn't justified yet.
What's the difference between criterion b and criterion c in myp maths?
Criterion B (Investigating Patterns) rewards finding, describing and justifying a mathematical rule from a specific scenario. Criterion C (Communicating) rewards how clearly you present that work — notation, labelled diagrams, logical flow and a coherent line of reasoning a stranger could follow without help.
| Criterion | Focus | Key question it answers |
|---|---|---|
| B — Investigating Patterns | Finding & proving the rule | Is your generalisation true and justified? |
| C — Communicating | Presentation & clarity | Can a reader follow your logic unaided? |
| D — Applying in Real-World Contexts | Relevance & reflection | Does the maths connect to a real situation? |
| A correct generalisation written messily can still lose marks — but under Criterion C, not B. |
How many marks is criterion b worth and what do the levels mean?
Criterion B is marked out of 8, split into four level bands (1–2, 3–4, 5–6, 7–8). Lower bands reward describing patterns and simple rules; the top band (7–8) requires generalisations that are correctly justified using appropriate mathematical language and shown to work for further cases.
Rough level guide (check your school's exact task-specific clarifications):
- 1–2: describes patterns, limited working.
- 3–4: describes a rule, some testing.
- 5–6: correct generalisation, tested, mostly justified.
- 7–8: generalisation justified and applied to a further, more complex situation.
Structuring & Writing the Investigation
What should the structure of an myp maths investigation look like?
A clean structure runs: introduce the problem, present organised data (a table works well), describe the pattern, form a rule, test the rule, justify it algebraically, then extend or reflect. Keep each section short and labelled — examiners are marking against criteria, not reading for style.
I tell students to literally use headings: Introduction, Data, Pattern, Rule, Testing, Justification, Extension. It looks basic but it makes it impossible for a moderator to miss where your generalisation actually is — which matters more than people expect.
How do you find a pattern if you're stuck on the task?
Start smaller than the task suggests — build the first 3 or 4 cases by hand before guessing anything. Put results in a table, look at the differences between consecutive terms (constant difference usually means linear; changing difference often means quadratic), then test your guess on a case you haven't drawn yet.
Worked example: A task asks how many matchsticks build a row of n triangles.
n=1 → 3, n=2 → 5, n=3 → 7.
Difference is constant (+2), so the rule is linear: .
Test n=4: predicted 9, drawn count 9. Confirmed.
Justify: each new triangle shares one side with the previous one, so it only adds 2 new matchsticks instead of 3.
How do you write a good generalisation using algebra?
Write your rule using proper algebraic notation with a defined variable (e.g. 'let n = number of terms'), not just a formula with unexplained letters. State it clearly as an equation, then immediately show it satisfies at least one case beyond your original data set.
Common mistake: students write with no definition of n anywhere, so a reader has to guess what it means. Always define your variable in a full sentence first — 'Let represent the number of matchsticks when there are n triangles' — then give the formula.
What common mistakes lose criterion b marks?
The most common losses: stopping at the pattern description without generalising algebraically, testing the rule only on data already used to find it, and giving a generalisation with no justification at all. Examiners consistently mark down investigations that are correct but unexplained.
Common mistake checklist:
- Testing on the same numbers used to spot the pattern (not a real test).
- Undefined variables in the formula.
- Jumping straight from a table to a formula with no working shown.
- No attempt to explain why the rule holds, even briefly. Fixing just the justification step alone typically moves a script up one full level band.
Should you use technology like graphing software in the investigation?
Yes, if it strengthens your evidence — plotting data points to confirm linearity, or using a spreadsheet to test your rule across many cases, both support Criterion B. But technology never replaces the algebraic justification itself; a graph shows a rule looks right, it doesn't prove why it's true.
Quick tip: if you use software, screenshot the output and label it, then write one sentence linking it back to your generalisation. An unlabelled graph dropped into the investigation earns you nothing under Criterion B — moderators need the connection spelled out.
Getting a Level 7-8 & Studying for It
What separates a level 7-8 investigation from a level 5-6 one?
A level 5-6 investigation has a correct, tested generalisation. A level 7-8 investigation has that same rule fully justified with sound mathematical reasoning, then successfully applied to a further or more complex related situation — showing the student understands why the rule works, not just that it does.
In fifteen years of marking these, the gap is almost never ability — it's that students run out of time before the extension step. Budget for it from the start: don't spend three pages describing the pattern and leave the justification as an afterthought.
How long should an myp maths investigation be?
There's no official IB page count for MYP investigations — schools set their own task-specific expectations, often 4–8 pages. Length matters far less than density: a tight 4-page investigation with a justified generalisation beats a padded 10-page one that never gets past describing the pattern.
Ask your teacher for the task-specific clarification sheet before you start — it tells you exactly what a level 7-8 response looks like for that particular task, which generic advice never can.
How can students revise or prepare for writing investigations?
Practise past investigation tasks under timed conditions, then mark your own draft against the actual Criterion B strand descriptors before showing a teacher. On RevisionPrep, MYP Mathematics Topical Worksheets and Revision Notes cover the sequence and pattern skills — arithmetic, geometric and quadratic patterns — that most investigation tasks draw on.
For Parents
How can parents support their child with an myp maths investigation?
The single most useful thing a parent can do is ask 'why does that rule work?' rather than checking the arithmetic — Criterion B rewards reasoning, not just a correct answer. Encourage your child to explain their generalisation out loud before submitting; if they can't, it isn't finished yet.
You don't need to know the maths yourself to help here. Asking your child to talk you through their reasoning step by step often reveals the gap in justification faster than any amount of re-checking numbers.
Do myp investigation grades matter for dp subject choices later?
MYP Criterion B performance doesn't feed directly into DP grades, but it's a genuine early signal — students who struggle to justify generalisations in MYP 4-5 often find DP Mathematics AA's proof-heavy content and internal assessment demanding without more practice. It's worth taking seriously as preparation, not just as a grade.
MYP Maths Investigation: Criteria at a Glance
| Criterion | Focus | Marks out of |
| B — Investigating Patterns | Finding & justifying the rule | 8 |
| C — Communicating | Clarity, notation, logical flow | 8 |
| D — Applying in Real-World Contexts | Relevance, reasoning, reflection | 8 |
For structured practice on patterns, sequences and algebraic generalisation before your next investigation, see the MYP Mathematics Revision Notes and Topical Worksheets on RevisionPrep.