Statistics and Probability
MYP5 Extended — Statistics and Probability
This is the topic where careless arithmetic costs more marks than not knowing the theory. Almost every question here is really testing three things: can you read the diagram correctly, can you use the right formula for experimental vs theoretical probability, and can you write a conclusion in a full sentence instead of just a number. Get those three habits right and this topic becomes free marks.
Overview
Statistics and Probability in MYP5 Extended splits into two connected worlds: descriptive statistics (organising and summarising data with graphs, averages and spread) and probability (predicting chance events, and checking predictions against real experimental results). The exam bank shows a strong bias towards quality-control style scenarios — dice, bottles, machines — where you calculate an experimental probability, compare it to a theoretical one, and explain the gap.
- Descriptive statistics answers 'what does this data set look like?' — box plots, histograms, cumulative frequency curves, mean/median/mode, range/IQR/standard deviation.
- Probability answers 'how likely is this event?' — theoretical probability from counting outcomes, experimental probability from real trials, and rules for combining events (AND/OR, independent/dependent).
- The two worlds meet in every quality-control question: you collect data (organise it), calculate a relative frequency (statistics), then compare it to a theoretical model (probability).
The shape of the chapter
Command term guidance
| Command term | What it demands | AO | Mark-earning move |
|---|---|---|---|
| Calculate | Obtain a numerical answer showing the relevant working — a bare answer with no formula shown loses method marks. | Knowing and using | Write the formula first, substitute values, then compute — each stage can carry its own mark. |
| State | Give a short answer with no justification needed — usually 1 mark, don't over-explain. | Knowing and using | One line, no working required. |
| Deduce | Reach a conclusion using given information plus a logical step — you must show the reasoning link, not just the result. | Applying and reasoning | State what you compared and what the comparison shows. |
| Justify | Give valid reasons or evidence to support a statement — a numerical answer alone earns zero if the reasoning is missing. | Applying and reasoning | Reference the specific numbers that support your claim. |
| Explain | Give a detailed account including reasons or causes — examiners want the 'because', not just the 'what'. | Communicating | Link cause to effect in a full sentence. |
Key point
Overview