Purpose: Numeracy, often defined as having an understanding of basic mathematical and probability concepts, is a component of the model of general health literacy. However, the construct of health numeracy remains poorly developed. In this study we empirically determine the domains of numeracy relevant to patients in the health care setting.

Methods: Focus groups were conducted. Participants included primary care patients, 40-74 years of age, who were English speaking. Focus groups were stratified by gender and level of formal education. The focus group guide lead a discussion regarding the use of numbers in everyday life and in health care. Numeric data from clinical trials was presented as a basis for discussing the use of numbers in the communication of scientific evidence. Sessions were audio and videotaped and transcribed verbatim for analysis; two investigators independently coded each transcript with a third investigator resolving discrepancies that remained after discussion.

Results: Six focus groups were conducted. In consideration of the cognitive and affective domains that emerged from the focus groups, a conceptual model was developed (Figure). The model can be represented as a pyramid. The base of the model consists of basic mathematic skills. Upon this base sits the applied health numeracy domain. At the apex of pyramid is interpretive health numeracy. In general, more complex cognitive processes are required as one moves from the base of the model to the apex. However, any given health task may require skills across the three domains. Influencing the application of basic, applied, and interpretive skills are domains of positive or negative affect. Our model recognizes the influence of affective domains in the use of quantitative information. Feelings, emotions, and attitudes contribute to a person's desire and ability to use numeracy skills in health.

Conclusion: The construct of health numeracy could be more broadly defined than has been common in the health services literature to date. In order to effectively use numeric information, a person must have basic math, applied numeracy, and interpretive numeracy skills to draw upon. Consideration of the interaction of these skills with psychological factors can help us to design stronger interventions in support of participatory and shared decision making models of health care.