Chart Selection
Different data calls for different pictures. Using the wrong one can mislead.
A histogram shows the distribution of a single continuous variable, using touching bins to reveal shape. A bar chart compares distinct categories with gaps between bars.
A scatterplot maps the relationship between two continuous variables. A box plot summarizes the five-number summary (minimum, Q1, median, Q3, maximum) and spots outliers.
| Chart | Best For |
|---|---|
| Histogram | Distribution shape |
| Bar chart | Category comparison |
| Scatterplot | Two-variable relationship |
| Box plot | Five-number summary |
| Line graph | Trends over time |
Visual Traps
Visualizations can deceive even with accurate data. A truncated y-axis starts above zero, making small differences look dramatic.
Other tricks include inconsistent scaling, cherry-picked time windows, and 3D effects that distort volume perception.
Common pitfall: Using a bar chart with a truncated axis to compare similar values. A bar chart is only honestly interpretable when its vertical axis begins at zero.
Always inspect where a chart's axis starts before trusting its visual impact.