Numeracy Understanding in Medicine Instrument - A Measure of Health Numeracy Developed Using Item Response Theory

Sep 25, 2026

Uploaded by Ben

Health numeracy is defined as the ability to understand and apply numerical information—numbers, tables, graphs, probabilities, and statistics—so people can communicate effectively with health care providers, manage their own health, and participate in medical decisions. The Numeracy Understanding in Medicine Instrument (NUMi) was developed using item response theory scaling methods, forming a 20-item test from an item bank and evaluating construct validity against established literacy and achievement measures. Results support NUMi as a robust health numeracy measure for research and clinical use.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages15

Reading Time38 min

AccessFree to download

Background and Objective

Instrument Development Using Item Response Theory

Construct Validity and Participant Samples

Results and Key Psychometric Findings

Limitations and Conclusions

The Numeracy Understanding in Medicine Instrument: A Measure of Health Numeracy Developed Using Item Response Theory Marilyn M. Schapira, MD, MPH, Cindy M. Walker, PhD, Kevin J. Cappaert, MA, Pamela S. Ganschow, MD, Kathlyn E. Fletcher, MD, MA, Emily L. McGinley, MS, MPH, Sam Del Pozo, MA, Carrie Schauer, BSW, Sergey Tarima, PhD, Elizabeth A. Jacobs, MD, MAPP | 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 a 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), theMedical 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. Key words: decision aids; shared decision making; risk communication; risk perception; health literacy. (Med Decis Making 2012;32:851–865) | | --- | --- | Received 28 May 2011 from the Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania (MMS); Department of Educational Psychology, University of Wisconsin–Milwaukee, Milwaukee, Wisconsin (CMW, KJC); Department of Medicine, John H. Stroger Jr. Hospital of Cook County and Rush University Medical Center, Chicago, Illinois (PSG, SDP); Department of Medicine, Clement J. Zablocki VA Medical Center, and Medical College of Wisconsin, Milwaukee, Wisconsin (KEF); Center for Patient Care and Outcomes Research, Medical College of Wisconsin, Milwaukee, Wisconsin (ELM, CS); Institute of Health and Society, Medical College of Wisconsin, Milwaukee, Wisconsin (ST);Department of Medicine, University of Wisconsin, Madison, Wisconsin (EAJ) . This study was funded by the National Cancer Institute of the National Institutes of Health (NCIR01CA115954). The work was presented atthe 2010 annual meeting of the Society for Medical Decision Making, Toronto, Canada. The REDCap database used in this work was supported by a Clinical and Translational Science Institute grant (1UL1-RR031973-01). The study was funded by the National Cancer Institute. The funder did not have a role in the collection, analysis, or interpretation of the data. Revision accepted for publication 15 March 2012 . 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 healthcare providers, take care of one’s

FAQs

What does the Numeracy Understanding in Medicine Instrument (NUMi) measure?

NUMi measures health numeracy, defined as the ability to understand and apply numerical information such as numbers, tables, graphs, probabilities, and statistics in health communication and decision making.

How was NUMi developed in this study?

NUMi was developed using item response theory scaling methods. A 20-item test was created from a numeracy question item bank, with items calibrated using responses from 1000 participants using a 2-parameter model.

What evidence supports NUMi’s validity and usefulness?

Construct validity was assessed by comparing NUMi scores with established measures of print and numeric health literacy, mathematic achievement, and cognitive aptitude. NUMi performance showed strong to moderate correlations with multiple referenced tests, and the instrument is recommended for research and clinical settings.

Sep 25, 2026

Uploaded by Ben