Numeracy

Definitions and Prevalence

In 2000, the Department of Health and Human Services defined health literacy as the skills needed to “obtain, process, and understand basic health information and services for approximate health decisions.” The National Center for Education Statistics (NCES), as part of the U.S. Department of Education's Institute of Education Sciences (IES), collects, analyzes, and publishes statistics on education and public school district finance information in the United States. The NCES in its Adult Health Literacy Survey in 1993 defines numeracy or quantitative literacy as “the knowledge and skills required to apply arithmetic operations, either alone or sequentially, using numbers embedded in printed material (e.g., balancing a checkbook, completing an order form).” In 2003, more than 19,000 adults participated in the national-and state-level assessments, representing the entire population of U.S. adults who are aged 16 and older, most in their homes and some in prisons from the 50 states and the District of Columbia. Approximately 1,200 inmates of federal and state prisons were assessed to provide separate estimates of literacy for the incarcerated population. The National Adult Literacy Survey (NALS), a nationally representative household survey administered by the NCES, showed that 22% of all American adults surveyed exhibited the lowest level of numeracy. The prevalence of below basic numeracy skills is associated with race/ethnicity: 13% of whites, 47% of blacks, and 50% of Hispanics exhibit below basic numeracy skills.

Health Numeracy and Measures of Numeracy

Health numeracy is emerging as an important concept and a component of health literacy. Use of health numeracy is increasing in health communication, for much of the health information has been provided to patients and written in numbers—such as diagnostic test results and treatment, prognosis, and medication regimens. For the majority of the medical decision making, when discussing risks and benefits, providers use simple ratios, probabilities, and estimates to communicate with patients. Numeracy is assessed by different measures and has been associated with poor outcomes (e.g., diabetes, nutrition, obesity, and asthma). Lower numeracy has been associated with increased medicine errors and increased hospitalizations. The original Test of Functional Health Literacy in Adults (TOFHLA) in 1995 included 17 questions that measured numeracy. Lisa Schwartz and colleagues and Isaac Lipkus and colleagues introduced and modified comprehensive numeracy scales, which measured simple numeracy skills of percentages, proportions, and frequencies.

Individual quantitative competencies can be categorized into three basic levels: (1) basic computation, (2) estimation, and (3) statistical literacy. [Page 826]Basic computation includes number recognition and comparison, arithmetic, and use of simple formulas. The TOFHLA screening test and the NALS include quantitative problems ranging from abstract problem solving to proportions and frequencies using medical scenarios, such as pill count, understanding sliding scale prescriptions, and nutrition labels. Estimations are used for quick calculations to estimate medication dosage, such as insulin units in diabetes. Statistical literacy is an understanding of concepts such as chance and uncertainty, sampling variability, and margins of errors. A large variety of medical scientific information is in forms of graphics with scales, bars, ratios, and so on, which might help patients understand epidemiological distribution of any disease, chances and uncertainty associated with a disease occurrence, and outcome or use in medical decision making for choice of treatment.

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