Paper I - Data Interpretation
Data Interpretation tests extracting and comparing numerical information from tables, bar and line graphs, pie charts and mixed displays. The mathematics is usually simple; marks are lost in reading axes, units and bases.
Core rules
- Read the title, units, legend, scale, and whether values are totals or percentages.
- Percentage of total = part divided by total, times 100; percentage change = (new minus old) divided by old, times 100.
- Percentage points measure the difference between two percentages; percent measures relative change.
- For pie charts, share = value/total times 100%, and angle = value/total times 360 degrees.
- Compare ratios by cross-multiplying or converting to a common base; do not compare raw counts when totals differ.
Worked example
A table shows a college had 400 students in 2022 and 500 in 2023; women were 40% in 2022 and 45% in 2023. Women rose from 160 to 225, an increase of 65, or 40.6% (65/160). The share rose by 5 percentage points, not 5%. Both statements are true but answer different questions.
Traps that cost marks
Reading a line graph's slope as absolute change when the y-axis is truncated; averaging percentages without weighting; confusing percent and percentage points; ignoring 'approximately'.