The Numeracy Understanding in Medicine Instrument

Abstract

Background Health numeracy can be defined as the ability to understand medical information presented with numbers, tables and graphs, probability, and statistics and to use that information to communicate with one’s health care provider, 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 (IRT) 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% Non-Hispanic white, and 42% Non-Hispanic black. Forty-one percent (41%) had no more than a high school education. The mean score on the NUMi was 13.2 (SD 4.6) with a Cronbach’s alpha of 0.86. Difficulty and discrimination IRT 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 WRAT-arithmetic test (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.

Development and Validation of the Numeracy Understanding in Medicine Instrument Short Form

“…The development and validation methods used for the 20-item NUMI have been previously reported [1]. In summary, the NUMi was developed using item response theory scaling methods.…”

“…Responses to test items were analyzed using a 2-parameter logistic (2-PL) IRT model to determine the difficulty and discrimination parameters for each item. Goodness of fit statistics found the 2-parameter model to fit our data better than a 1 parameter model in the validation study of the 20 item NUMi[1]. Based on an item level analysis and the distribution of content across domains, a 20-item test was formed and validated against existing measures of health print literacy, health numeracy, mathematic achievement, cognitive ability, and education.…”

“…Numeracy can be defined as one's ability to understand and use numeric information conveyed in numbers, tables and graphs, probability, and statistics in the context of caring for your health and making health care decisions[1]. The hierarchical nature of health numeracy skills has been well described and includes a range of skills, from basic arithmetic to a more conceptual understanding of concepts such as risk, probability, and statistics[2-5].…”

Clinician Numeracy: The Development of an Assessment Measure for Doctors

“…Some tests aimed to assess basic numeracy in the general public (Williams et al 1995;Baker et al 1999;Weiss et al 2005), while others investigated statistical literacy (Schwartz et al 1997;Schwartz et al 2005;Peters et al 2007;Cokeley et al 2012, Weller et al 2013, and a few focused on numeracy and the management of a particular disease (Estrada et al 2004;Apter et al 2006;Huizinga et al 2008). Although the Numeracy Understanding in Medicine Instrument (Schapira et al 2012) tests a range of constructs, its test material-in common with other assessments developed for patients-was very simple, as observed by Vacher and Chavez (2009). None of these tests were suitable for assessing clinician numeracy.…”

Impact of numeracy on parental self-efficacy and treatment outcome of children on complex diets.

“…But numeracy, and health numeracy, are broader concepts in both mathematics and life-skills applications. Several authors have acknowledged the broader picture of numeracy (R. L. Rothman, Montori, V. M., Cherrington, A., Pignone, M.P., 2008), (Marilyn M. Schapira et al, 2012), (Ancker & Kaufman, 2007), (Montori & Rothman, 2005), but none has embraced the entire scope of numeracy in a health context. Golbeck provides the most comprehensive definition of health numeracy: "the degree to which individuals have the capacity to access, process, interpret, communicate, and act on numerical, quantitative, graphical, biostatistical, and probabilistic health information needed to make effective health decisions" (Golbeck et al, 2005).…”