The meaning of numbers in health: exploring health numeracy in a Mexican-American population.

BACKGROUND: Health numeracy can be defined as the ability to use numeric information in the context of health. The interpretation and application of numbers in health may vary across cultural groups. OBJECTIVE: To explore the construct of health numeracy among persons who identify as Mexican American. DESIGN: Qualitative focus group study. Groups were stratified by preferred language and level of education. Audio-recordings were transcribed and Spanish groups (n = 3) translated to English. An analysis was conducted using principles of grounded theory. PARTICIPANTS: A purposeful sample of participants from clinical and community sites in the Milwaukee and Chicago metropolitan areas. MAIN MEASURES: A theoretical framework of health numeracy was developed based upon categories and major themes that emerged from the analysis. KEY RESULTS: Six focus groups were conducted with 50 participants. Initial agreement in coding was 59-67% with 100% reached after reconciliation by the coding team. Three major themes emerged: 1) numeracy skills are applied to a broad range of communication and decision making tasks in health, 2) affective and cognitive responses to numeric information influence use of numbers in the health setting, and 3) there exists a strong desire to understand the meaning behind numbers used in health. The findings informed a theoretical framework of health numeracy. CONCLUSIONS: Numbers are important across a range of skills and applications in health in a sample of an urban Mexican-American population. This study expands previous work that strives to understand the application of numeric skills to medical decision making and health behaviors.

The numeracy understanding in medicine instrument: a measure of health numeracy developed using item response theory.

BACKGROUND: Health numeracy can be defined as the ability to understand and apply information conveyed with numbers, tables and graphs, probabilities, and statistics to effectively communicate with health care providers, take care of one's health, and participate in medical decisions. OBJECTIVE: To develop the Numeracy Understanding in Medicine Instrument (NUMi) using item response theory scaling methods. DESIGN: A 20-item test was formed drawing from an item bank of numeracy questions. Items were calibrated using responses from 1000 participants and a 2-parameter item response theory model. Construct validity was assessed by comparing scores on the NUMi to established measures of print and numeric health literacy, mathematic achievement, and cognitive aptitude. PARTICIPANTS: Community and clinical populations in the Milwaukee and Chicago metropolitan areas. RESULTS: Twenty-nine percent of the 1000 respondents were Hispanic, 24% were non-Hispanic white, and 42% were non-Hispanic black. Forty-one percent had no more than a high school education. The mean score on the NUMi was 13.2 (s = 4.6) with a Cronbach α of 0.86. Difficulty and discrimination item response theory parameters of the 20 items ranged from -1.70 to 1.45 and 0.39 to 1.98, respectively. Performance on the NUMi was strongly correlated with the Wide Range Achievement Test-Arithmetic (0.73, P < 0.001), the Lipkus Expanded Numeracy Scale (0.69, P < 0.001), the Medical Data Interpretation Test (0.75, P < 0.001), and the Wonderlic Cognitive Ability Test (0.82, P < 0.001). Performance was moderately correlated to the Short Test of Functional Health Literacy (0.43, P < 0.001). LIMITATIONS: The NUMi was found to be most discriminating among respondents with a lower-than-average level of health numeracy. CONCLUSIONS: The NUMi can be applied in research and clinical settings as a robust measure of the health numeracy construct.