How Point (Single-Probability) Tasks Are Affected by Probability Format, Part 2: A Making Numbers Meaningful...

Background. The Making Numbers Meaningful review is intended to create guidance on the effect of data presentation format on comprehension of numbers in health. Purpose. This article (one of a series) covers research studying so-called "point tasks," in which a reader examines materials to obtain information about single probabilities. The current article presents evidence on the effects of data presentation format on probability perceptions and feelings, health behaviors and behavioral intentions, trust, preference, and discrimination outcomes. Data Sources. MEDLINE, Embase, CINAHL, the Cochrane Library, PsycINFO, ERIC, ACM Digital Library; hand search of 4 journals. Study Selection. Manual pairwise screening to identify experimental and quasi-experimental research that compared 2 or more formats for presenting quantitative health information to patients or other lay audiences. This article reports 466 findings of probability communication from 161 articles. Data Extraction. Pairwise extraction of information on stimulus (data in a data presentation format), task, and outcomes. Data Synthesis. Moderate to strong evidence is available on the effects of several format interventions to influence probability perceptions and feelings, including the 1-in-X number format, foreground-only (numerator-only) icon arrays, bar charts, anecdotes, framing, and verbal probabilities. However, only 3 (the 1-in-X effect, anecdotes, and framing) had moderate to strong evidence of influencing health behaviors and behavioral intentions. Research on patient preferences for numerical, graphical, and verbal formats yielded only weak evidence. Conclusions. The link between probability perceptions/feelings and health behaviors is not strongly reflected in the evidence about communicating numbers because many communication-focused studies measure short-term response rather than longer-term behaviors. Also, research into patient preferences for numerical, graphical, and verbal formats has not yielded strong evidence suggesting stable and predictable preferences.

Formatting a probability as 1 in X, using a foreground-only icon array, adding anecdotes to numbers, and gain-loss framing all affect probability perceptions and feelings.The evidence on communicating numbers to influence perceptions is far stronger than the evidence on using it to change health behavior or behavioral intention.Only weak evidence is available on patient preferences for verbal, graphical, and numerical probability formats.