MYP · Mathematics MYP Year 2
Statistics – Averages and Analysis
MYP Mathematics framework — Statistics strand: averages, spread and grouped-data analysis
23 min readStandardCore data-handling unit — assessed mainly under Criterion D (applying maths in real-life/statistical contexts) with Criterion B method marks for grouped-data calculations; recurs in almost every end-of-unit test on statistics.
Averages tell you almost nothing sitting on their own — a mean of 23 could hide a class where everyone scored around 20, or one where half the class failed and a handful aced it. This chapter is about squeezing the real story out of a set of numbers: grouping raw data sensibly, working backwards from an average to rescue a missing value, reading a box plot in one glance, and — the skill examiners reward most and mark down hardest — actually comparing two datasets instead of just parking two numbers next to each other.
Overview — The Shape of the Chapter
Why grouping, missing values and comparisons all sit in one chapter
- Raw lists of 20–30 numbers are unreadable — grouping into class intervals turns them into a table you can actually interpret at a glance.
- Every 'average' (mean, median, mode) answers a slightly different question about what's typical — mixing them up is the single most common error across this whole unit.
- A statistic means nothing until it's compared: '23 out of 50' sounds mediocre until you learn the other class averaged 15 — or brilliant until you learn they averaged 40.
- Box plots and IQR exist because averages alone hide spread — two classes can share an identical median and still have completely different levels of consistency.
The shape of the chapter
Command terms that actually appear on this topic
| Command term | What it demands | AO | Mark-earning move |
|---|---|---|---|
| State / Identify | Give a specific value or fact straight from the data — no working or justification required. | Knowing | 1 mark for the correct value alone; writing a full interval where a single number was wanted (e.g. '20–29' instead of '24.5') scores 0. |
| Calculate | Produce a numerical answer, showing the method used to get there. | Applying | Method mark for correct working even if the final figure is arithmetically wrong; a bald correct-looking answer with no working can lose the method mark if it's actually wrong. |
| Describe | Give a written account of a pattern or relationship in the data. | Applying | Needs a full sentence about a trend (e.g. 'as width increases, frequency tends to increase') — a single word like 'positive' scores 0. |
| Explain | Give reasons that justify a statement — the 'why', not just the 'what'. | Reasoning | A correct fact with no reasoning attached earns 0 on an Explain mark; the reasoning IS the mark. |
| Compare | Relate two or more data sets directly to each other using a comparative word. | Reasoning | Two separate correct statements about each dataset, with no linking word (higher/lower/more consistent), typically lose the comparison mark entirely. |
Key point
A grouped-data mean is always an ESTIMATE — you've swapped every real score for its class midpoint. Never claim it's 'the exact mean' unless you also have the raw data to check.
Overview