| Qualitative, one variable | Simple bar chart; pie chart (parts of a whole, few categories) | Bars separated; pie sectors = % × 3.6° |
| Qualitative, two variables | Multiple (clustered) or component (stacked) bar chart | Compare within and between groups |
| Quantitative, one variable | Histogram (area ∝ frequency; adjacent bars), frequency polygon (midpoints joined), stem‑and‑leaf, box‑and‑whisker | Unequal class widths → plot frequency density |
| Cumulative | Ogive: "less than" (rising) and "more than" (falling) curves; they intersect at the median | Read percentiles |
| Time series | Line chart; epidemic curve is a histogram by onset date | Consistent intervals |
| Two quantitative variables | Scatter diagram ± regression line | Shape, outliers |
| Geographical | Spot map, choropleth (shaded by rate) | Use rates, not counts, for choropleths |
| Rates of disease by age/sex | Population pyramid (Concept 41) | Bars horizontal, males left |
| Proportions over categories | Pictogram (lay audiences) | Easy to distort |