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MYP Maths: Scatter Graphs & Correlation FAQ
Answered by RevisionPrep's IB Educators
Scatter graphs trip up MYP 4-5 students not because the maths is hard, but because the wording of the question changes what's expected. Answered by RevisionPrep's IB Educators, here's exactly how to read, plot and interpret correlation questions the way MYP examiners actually mark them.
Concept & How to Answer
How do you answer MYP Maths questions on scatter graphs & correlation?
Plot every point accurately, describe the correlation using strength and direction (strong/weak, positive/negative), then link your answer to the real-world context given in the question. MYP examiners mark under Criterion D for exactly this — using mathematics to justify a conclusion about the actual data, not just describing a shape.
A typical mark scheme wants three things in order:
- Correct scatter graph or reading from a given one.
- Correct description: e.g. 'strong positive correlation'.
- A context sentence: 'as study time increases, test scores tend to increase too'.
Quick tip: if the question says 'comment on the relationship', you must mention both strength AND direction, or you lose a mark even with a correct graph.
How do you describe correlation in words for MYP Maths?
Describe two things: direction (positive, negative or no correlation) and strength (strong, moderate or weak), based on how tightly points cluster around a line. 'Strong positive correlation' means points rise together and sit close to a trend line; 'weak negative' means a loose downward scatter.
Quick reference wording:
- Strong positive: points rise together, tightly clustered.
- Weak positive: points rise together, loosely scattered.
- Strong negative: points fall together, tightly clustered.
- No correlation: no visible pattern at all.
Common mistake: writing 'positive correlation' without a strength word — most MYP criteria expect both.
How do you draw a line of best fit in MYP Maths?
Draw a straight line through the data so roughly equal numbers of points sit above and below it, following the overall trend rather than joining dots. It doesn't need to pass through the origin or touch every point — it should just represent the general direction of the correlation.
Worked example: given points (1,3), (2,5), (3,6), (4,9), (5,10), plot them, then draw a straight line starting near (0,2) and ending near (5,11) — passing close to the middle of the cluster. From this you can estimate the y-value at x = 6 by extending the line, which is exactly what 'interpolation' and 'extrapolation' questions ask you to do.
What's the difference between interpolation and extrapolation?
Interpolation means estimating a value inside the range of your original data — this is usually reliable. Extrapolation means estimating a value outside that range, using the line of best fit extended beyond the plotted points — this is far less reliable and examiners expect you to say so.
Common mistake: students give an extrapolated value with full confidence. In MYP Criterion D, you're often asked to comment on the reliability of a prediction — always flag extrapolation as an assumption, e.g. 'this assumes the trend continues beyond the data collected, which may not be true.'
Difficulty & Grades
Is MYP scatter graphs & correlation hard?
Not conceptually hard — the plotting and description skills are straightforward once practised. Where students lose marks is in the interpretation: linking correlation to causation incorrectly, or forgetting to reference the real-world context in their conclusion, which is exactly what Criterion D rewards.
In my experience marking MYP work, the grade 7 answers aren't the ones with the neatest graphs — they're the ones that write a full sentence linking the statistic back to the scenario, e.g. 'this suggests but doesn't prove that increased advertising spend causes higher sales.'
Why do students lose marks on correlation questions?
The most common reason is confusing correlation with causation — stating that one variable 'causes' the other when the data only shows they change together. Examiners also deduct marks for vague description ('there is a relationship') instead of specific direction-and-strength language.
3 things to check before submitting:
- Have you named both direction and strength?
- Have you avoided the word 'causes' unless the question explicitly asks about causation?
- Have you tied your conclusion back to the specific context (not just 'x' and 'y')?
Does correlation mean causation in MYP Maths?
No — this is one of the most heavily tested ideas in this unit. A strong correlation only shows two variables move together; it doesn't prove one causes the other. A classic MYP example is ice cream sales and drowning rates, both driven by hot weather, not by each other.
Quick tip: when a question asks 'does this data prove X causes Y?', the safe, mark-worthy answer is almost always 'no — there could be another factor (a confounding variable) affecting both.'
Exam & Assessment Criteria
Which MYP assessment criterion covers scatter graphs?
Scatter graph and correlation tasks are usually assessed under Criterion D: Applying mathematics in real-life contexts. According to the IB's MYP: Mathematics guide, Criterion D asks students to identify relevant elements of authentic real-world situations, apply mathematics, and justify the degree of accuracy of a solution.
Criterion C (Communicating) can also apply if the question specifically credits how you present your graph, labels and units — so always label axes, include a title, and use a consistent scale.
What command terms come up in scatter graph questions?
Expect 'plot', 'describe', 'comment on', 'estimate' and 'justify'. Each demands something different: 'plot' wants accurate points on axes, 'describe' wants direction and strength in words, 'comment on' wants an evaluative sentence, and 'justify' wants reasoning tied to the data, not just a stated opinion.
| Command term | What examiners want |
|---|---|
| Plot | Accurate points, correct axes |
| Describe | Direction + strength |
| Estimate | A reasonable value using the line |
| Justify | Reasoning linked to the data itself |
How is correlation strength measured numerically?
In MYP 4-5, correlation strength is usually judged visually rather than calculated, but some extended classes introduce the correlation coefficient (r), where values close to +1 or -1 mean strong correlation and values near 0 mean little or no relationship.
Worked example: if r = 0.92, that's a strong positive correlation — points cluster tightly around an upward line. If r = -0.15, that's very weak (almost no) correlation, even though the sign is negative. Don't confuse a negative r with a 'bad' result — it just means the variables move in opposite directions.
Comparisons & Real-World Use
How does scatter graph work compare between MYP and DP Maths?
MYP focuses on plotting, describing correlation, and drawing a line of best fit by eye. DP Maths AA and AI build on this with the Pearson's correlation coefficient calculated by GDC, regression equations, and formal hypothesis testing — so MYP is the essential visual and conceptual groundwork for DP statistics.
| Stage | Focus |
|---|---|
| MYP 4-5 | Plot, describe, line of best fit by eye |
| DP AA/AI | Calculate r, regression line, GDC use |
If your child is heading into DP Applications and Interpretation, solid MYP correlation skills make the statistics unit noticeably easier.
Why does my child need to learn scatter graphs and correlation?
Because it's the foundation for statistical literacy used across DP subjects — Biology, Geography, Economics and both Maths courses all require reading and interpreting scatter data. It also directly builds the Criterion D skill of applying maths to authentic situations, which carries through the whole MYP programme.
This isn't a topic that disappears after the unit test — correlation reasoning reappears in DP internal assessments across several subjects, so getting the language ('strong', 'weak', 'no causation implied') solid now saves real time later.
Practice & Resources
What's the best way to practise scatter graph questions before a test?
Practise past-style questions that combine plotting, description and a real-world justification sentence — not just isolated plotting drills. On RevisionPrep, the MYP Mathematics topical worksheets group scatter graph and correlation questions with mark schemes so you can check your wording, not just your graph.
Quick tip: time yourself writing the interpretation sentence separately from the plotting — most students run out of exam time on the words, not the graph, because they haven't practised the sentence structure in advance.
Where can I find MYP Maths revision notes on statistics topics?
RevisionPrep's MYP Mathematics section has revision notes covering the full statistics strand, including scatter graphs, correlation, and the criteria language examiners look for, alongside topical worksheets and mock papers for timed practice.
For a parent checking progress, the clearest sign your child has this topic solid is whether they can explain, out loud, why a strong correlation doesn't prove causation — that single skill covers most of the marks lost across the unit.
MYP vs DP: Scatter Graphs & Correlation
| Stage | Focus | Tools used |
| MYP 4-5 | Plot, describe, line by eye | Graph paper / GDC optional |
| DP AA/AI | Pearson's r, regression equation | GDC required |
For guided practice on this exact unit, see RevisionPrep's MYP Mathematics revision notes, topical worksheets and mock papers on statistics.