[Show abstract][Hide abstract] ABSTRACT: 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.
No preview · Article · May 2012 · Medical Decision Making
[Show abstract][Hide abstract] ABSTRACT: 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.
To explore the construct of health numeracy among persons who identify as Mexican American.
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.
A purposeful sample of participants from clinical and community sites in the Milwaukee and Chicago metropolitan areas.
A theoretical framework of health numeracy was developed based upon categories and major themes that emerged from the analysis.
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.
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.
Full-text · Article · Feb 2011 · Journal of General Internal Medicine
[Show abstract][Hide abstract] ABSTRACT: Purpose: To develop a test of a measure of health numeracy that is based on an empirically derived framework, cross-culturally equivalent for Hispanic and Non-Hispanic populations, and uses Item Response Theory scaling methods.
Method: A cross-cultural approach was used in the development of the Numeracy Understanding in Medicine Instrument (NUMi). Qualitative methods used to generate the item bank (n=110) included focus groups, convening of an expert panel, and cognitive interviews. Participants (n=1000) were recruited from community and clinical populations to test the items. A 2-Parameter IRT model was used for analysis of the first 500 respondents. Participants also responded to the Test of Functional Health Literacy in Adults-Short Form (S-TOFHLA) and a cognitive reasoning and aptitude test (Wonderlic). A sample (n=200) of participants were also administered the Lipkus numeracy scale and a mathematic achievement test (WRAT-M).
Result: Of the first 500 participants 50% were White and 40% were Black. Over 30% were Hispanic and 40% had a high school level education. Based upon the IRT parameters of difficulty (range of -3.0 t0 3.0) and discrimination (range of 0 to 3.0), 20 items were chosen to form the NUMi. The most difficult items in each domain assessed the following skills: 1) Determining how many 500 mg pills add up to 3 grams (number sense), 2) interpreting a risk of 2/1000 in a pictograph (tables and graphs), 3) interpreting a relative risk reduction (probability), and 4) interpreting the meaning of a p-value that is < 0.05 (statistics). The Test Information Function peaked at a difficulty level of -1.0 indicted that the test is most discriminating for people with lower than average health numeracy. Test performance was positively associated with cognitive reasoning (0.79) and print health literacy (0.54).
Conclusion: The NUMi is a 20 item paper and pencil test that measures an empirically based construct of health numeracy. In future work, a computerized adaptive test will be developed in which items are selected based upon the ability of the respondent leading to a shorter test that will reduce respondent burden and allow for oral or print administration. The NUMi will provide a feasible and valid assessment of health numeracy skills for use in both research and clinical settings.