Statistical numeracy for health: a cross-cultural comparison with probabilistic national samples.

BACKGROUND: Statistical numeracy is essential for understanding health-related risks and making informed medical decisions. However, this concept has not been investigated with probabilistic national samples or compared cross-culturally. We sought (1) to investigate differences in the level of statistical numeracy between 2 countries with different educational and medical systems-the United States and Germany; (2) to study the relationship between statistical numeracy and demographic characteristics such as age, sex, and education; and (3) to test whether a subjective measure of numeracy is a valid indicator of objective measures.
METHODS: In a survey of probabilistic, representative national samples in Germany and the United States, conducted in July and August 2008, we asked questions testing objective and subjective statistical numeracy.
RESULTS: German participants had higher numeracy skills than did US participants. On average, 68.5% (SE, 1.1%) and 64.5% (SE, 1.3%), respectively, of items testing objective numeracy were answered correctly. Subjective estimates of numeracy were a good indicator of the objective measures. There is a large gap in numeracy skills between persons with lower and higher educational levels, particularly in the United States.
CONCLUSIONS: Physicians should be aware that many patients may not understand all information relevant to making an informed decision. Fortunately, they can identify such patients and use nonnumerical presentation formats, such as graphical displays and analogies, to communicate important statistical information.