tufte-graphical-integritylisted

# Graphical Integrity ## Overview A graphic has integrity when the physical size of the marks on its surface is directly proportional to the numbers they stand for. Most distortions are not random: they systematically exaggerate the magnitude of recent change. Tufte's contribution is to make distortion measurable — the Lie Factor turns "this chart feels misleading" into a number you can compute and defend. **Sourcing note.** Tufte computes and publishes five Lie Factors in VDQI Ch. 2: fuel economy **14.8** (p. 57); the Time "In the Barrel" oil-price barrel **9.4** — +454% drawn as +4,280% (p. 62); the Washington Post oil derricks **9.5** — 708% drawn as 6,700% (p. 62); the shrinking family doctor **2.8** (p. 69); and **59.4** — "a record" — when the Time barrel is read as a volume, 27,000% vs. 454% (p. 71). Any other numeric figure in this skill is an illustrative derivation of the stated mechanism, labeled as such — never cite it as a Tufte-stated value. ## §1. The Lie Factor The single measurement that converts opinion into evidence: ``` Lie Factor = (size of the effect shown in the graphic) / (size of the effect in the data) ``` "Size of effect" is a percentage change: `(later − earlier) / earlier × 100`. Compute it once for the data, once for the printed marks (line lengths, bar heights, icon areas), then divide. **Thresholds:** | Lie Factor | Verdict | Action | |---|---|---| | 0.95 – 1.05 | Acceptable — ordinary plotting error only | Ship | | < 0.95 | Understates