Britta L . Anderson & Jay Schulkin

The research discussed in this volume stems, in part, from work on health literacy. Health literacy is “the degree to which individuals have the capacity to obtain, process, and understand basic health information and services needed to make appropriate health decisions” (nnlm.gov). When people hear the term health literacy, they may think of a patient’s ability to read medical information and understand medical terminology; however, health literacy not only includes literacy, but also numeracy. A broad and basic definition of numeracy is the ability to use and understand numbers. Terms related to, and often used synonymously with, numeracy include quantitative literacy, health numeracy, and statistical literacy. Table I.1 highlights several examples of how these terms have been defined in previous research and throughout this book. As shown in Table I.1, the terms used to describe numerical reasoning refer to a range of abilities, from the very basic (knowing which number is larger than another) to advanced (statistical terminology). We provide these examples to demonstrate the breadth of the concept at hand and encourage the reader to be mindful of the use of these terms throughout this book. Large national samples have found that there is a significant proportion of the population who have only basic numeracy skills or less (meaning partial mastery or no mastery of grade-level skills). For example, 47% of adults who completed the National Adult Literacy Survey (NALS) were in the lowest two (of five) levels of performance (Kirsch et al., 2002). A more recent national survey of adults found that 36% are at or below basic levels (Kutner et al., 2006). Deficits in basic numeric ability are not only found in the general population, but also in subgroups of highly educated individuals (e.g., Lipkus et al., 2001; Anderson et al., 2014). Along with basic numeracy, statistics is an essential part of the numeric language of medicine. However, unlike basic numeric abilities, statistics have not always had such a central role in medicine. The rise of statistical reasoning occurred due to the need to establish state records as well as catalog diseases, viruses, and plague events that impacted human and