GSET: Data Interpretation

The GSET Data Interpretation domain presents tables, bar and line charts, and infographics, then asks for rates, ratios, percentages, averages, and trends. Careful reading of labels and units is as important as calculation.

Core rules

• Read the title, axes, legend, units, and footnotes before computing.
• Identify the base for every percentage: percent change uses the earlier value; percent of total uses the whole.
• Distinguish percent from percentage points. A rise from 20% to 25% is 5 percentage points but a 25% relative increase.
• Use weighted averages for group rates; do not average percentages unless the group sizes are equal.
• Estimate first and eliminate choices whose magnitude is impossible.

Worked example

A table shows a company's revenue as $120 million in 2019 and $180 million in 2021. By what percent did revenue increase from 2019 to 2021? The change is 180 − 120 = 60. The base is the 2019 value, so the increase is 60 / 120 = 50%. A trap answer of 33.3% comes from dividing by 180, the later value. If the question instead asked "2021 revenue is what percent of 2019 revenue?", the answer would be 180 / 120 = 150%. The arithmetic is simple; the mark depends on choosing the right base.

Traps

• Reading a truncated axis as if it began at zero, exaggerating visual slopes.
• Adding percentages from different bases.
• Ignoring per-capita or per-unit qualifiers.
• Averaging subgroup rates without weighting by subgroup size.
• Confusing a total with an average.