Data questions test whether you can read what a display actually shows. Learn the checks that separate a correct read from a plausible wrong one.
Before any calculation, read the title, axes, scale and units. Then decide whether the question asks for an absolute figure, a share or a rate of change, since the largest change in each sense can belong to a different category. Write the formula you need, then compute.
Every chart or table has a frame: a title, labels, units, a time period and a source line. A large share of wrong answers come from skipping it. Spend the first ten seconds on the frame and the rest of the question becomes much simpler.
The table below is original. It shows store visits, in each region, for two consecutive years.
| Region | Year 1 | Year 2 |
|---|---|---|
| North | 12,400 | 13,640 |
| South | 8,000 | 8,400 |
| East | 5,600 | 6,720 |
| West | 4,000 | 3,600 |
| Total | 30,000 | 32,360 |
Every figure here was computed in Python before being written down. Note that the total rose by 2,360, and the regional changes add up to the same number: 1,240 plus 400 plus 1,120 minus 400. Cross-checks like that catch addition slips.
| What is asked | Formula | Example from the table |
|---|---|---|
| Absolute change | New minus old | East: 6,720 minus 5,600 = 1,120 |
| Percentage change | Change divided by old value | East: 1,120 divided by 5,600 = 20% |
| Share of total | Part divided by total | East in Year 2: 6,720 divided by 32,360 = 20.8% |
Percentage points are the difference between two shares, so East moving from 18.7% to 20.8% of the total is up about 2.1 percentage points. Mixing percentage points with percent change is one of the most common errors in data questions.
Data sets are dense, so you need a sensible way to avoid overworking. Estimate with round numbers whenever the options are far apart: 13,640 out of 32,360 is close to 14 out of 32, which is a little under 44%, and that already points to the 42% option. Use exact working only where options are close.
Keep calculations as ratios when you can. Comparing 1,120 over 5,600 with 1,240 over 12,400 is quicker as 1 in 5 against 1 in 10 than as two long decimals.
And use the structure of the question. Many sets ask three or four questions on one display, so spend your frame-reading time once and re-use it.
Data interpretation sits close to numerical reasoning, and the habits overlap. See numerical reasoning tips for estimation and percentages, and numerical reasoning test formats for what the displays look like in different tests. If you also face error-checking tasks, which compare two data sources, see error-checking tests.
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For a timed warm-up, try the free numerical reasoning practice test.
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It is the skill of reading tables, charts and graphs and answering calculation questions about them. It is usually part of numerical reasoning tests.
A percentage change compares a new value with an old one, while percentage points are the plain difference between two percentages. A share going from 18% to 24% is up 6 percentage points.
A scale that does not start at zero can make small differences look large. Read the axis labels before judging bar or line heights.
Read the title, units and legend first, then go straight to the part the question names. Estimate with round numbers when the options are far apart.
It depends on the test, so check your instructions. Practise mental estimation either way, since it speeds up elimination.
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