Visualizing Data
What this domain tests
This domain tests chart selection and honest presentation: choosing the form that fits the question and avoiding designs that exaggerate or hide the finding. Items ask which chart or setting is appropriate.
Core rules
- Comparison across categories: bar chart, sorted by value.
- Trend over time: line chart, with enough periods to show seasonality.
- Distribution: histogram or box plot.
- Relationship between two measures: scatter plot.
- Composition: stacked bar; avoid pie charts beyond about four slices.
- Cross-tabulation: heat map.
- Networks and entity links: link chart with consistent node symbols.
- Bar axes start at zero; line charts may be truncated only with clear labeling.
- Small multiples share a fixed scale so panels are comparable; titles state the finding, not the field name.
Worked example
Showing claim frequency by month for six regions. Reasoning: a pie of twelve months loses the trend, and a single line with six series becomes unreadable. Use small multiples - six panels of monthly frequency with one shared y-axis - and annotate the month a new vendor began receiving referrals. Shared scaling prevents a small region's noise from looking larger than a high-volume region's real change.
Traps that cost marks
- Truncated bar axes that make small differences look dramatic.
- Dual axes implying a relationship that is not established.
- Pie charts with ten categories.
- Charting counts when the question requires rates.