Module 3

Drawing honest charts: baselines, denominators, periods and what is left out

A chart can mislead without a single false number. It can start its axis at 90 so that a change of two points looks like a collapse. It can show the three months in which a trend looked bad, and not the three years in which it did not. It can compare the number of incidents in a large region and a small one, so that the large one looks worse whatever its rate. It can add a second axis, and draw two unrelated series so that they seem to move together. Each choice is easy to defend in isolation, and the combination can persuade a reader of something the data do not show. For a lawyer this is more than a matter of style. A chart used in evidence, in a regulatory submission or in advice to a client carries a duty of accuracy, and a chart in the other side’s bundle may need to be challenged. This module teaches the main ways in which charts mislead, how to draw an honest chart in each case, and how to read other people’s charts with suspicion that is fair. The Chart Honesty Check turns the rules into a checklist.

General education on visual communication for lawyers, using invented organisations, people, data and cases. It states common practice in simplified form and does not describe any one country's law or court rules, which differ and change; rules on exhibits, demonstrative aids, disclosure, candour and confidentiality in particular vary. The tools apply simple rules to descriptions and text that you supply. It is not legal advice, and it does not replace advice from a qualified lawyer on a real matter.