IB ESS Data Questions: Graphs, Calculations and Command Terms

28 Jul IB ESS Data Questions: Graphs, Calculations and Command Terms

For IB ESS data questions, start with the question and the evidence it asks you to use. A useful checklist is: identify the command term, read labels and units, select relevant evidence, and answer at the required depth. This is a tutoring checklist, not an official IB marking formula.

Read the data carefully

Check axes, scale, time period and location. Distinguish a total from a rate and a percentage from a percentage-point difference. Identify uncertainty or missing information when it is relevant to the question. A graph can show an association without establishing its cause.

Match the command term

• Describe: state the relevant pattern or characteristics.
• Explain: give reasons or a mechanism supported by the context.
• Discuss: develop a considered account of relevant arguments.
• Evaluate: weigh strengths and limitations and reach a supported judgment.

Use the actual question and its markscheme. There is no universal sentence count, word count or formula that guarantees a mark. Do not add a named case study or a feedback loop unless it helps answer the question.

Original practice exercise

These numbers and the task below were created for practice. They are not an IB question, a real dataset or an examiner-marked answer. A survey records 48 species at one sampling time and 30 at a later time using comparable methods. Describe the change.

A possible response is: “Recorded species richness decreased by 18 species, a 37.5% decrease relative to the first survey.” This describes the change; it does not establish why it happened. No official mark allocation is claimed.

Species richness counts species; it does not measure how evenly individuals are distributed among them. A richness comparison alone therefore cannot describe every aspect of biodiversity.

Percentage check: an illustrative increase in vegetation cover from 20% to 30% is 10 percentage points, or a 50% increase relative to the initial cover: (30 − 20) ÷ 20 × 100. State which measure you mean.

For temperature measured in Celsius, report a difference in degrees Celsius rather than treating the arbitrary Celsius zero as the basis for a percentage increase.

A quick checklist before you submit

• Have I used the correct variable, unit and time period?
• Have I supported the pattern with relevant values?
• Does my calculation show its working and reference value?
• Have I answered the command term rather than adding unrelated information?

Review your answer

Attempt the question before reading the markscheme, then record one specific error and practise another relevant question. Follow invigilator instructions about reading time and permitted writing or annotation. Use ESS command terms as a revision reference.

Practise with individual ESS support

In Marija’s online IB ESS SL and HL lessons, you can work on concepts, data interpretation and clear explanations. Request a free 20-minute trial lesson to discuss your priorities. For IA work, the investigation and submitted writing remain your own.

Official reference: IB ESS guide, first assessment 2026. Updated 19 October 2026.