Development and Validation of the Health Numeracy Test for Japanese Adolescents

Educating the public to interpret health-related numerical information is essential for informed decision-making. Japan’s national Courses of Study for elementary and secondary school health education provide limited specific content or instructional approaches for developing health numeracy. To address this gap, this study developed and validated a Health Numeracy Test for Japanese Adolescents based on existing definitions and frameworks. High school students in grades 10–12 participated in a web-based survey; of 870 participants, 620 were included in the analyses. The survey was administered online during class hours under teacher supervision. The test consists of 19 items and demonstrated an essentially unidimensional structure. Item response theory analyses showed adequate discrimination across items and high measurement precision, with the greatest precision observed in the lower range of health numeracy ability. The test demonstrated good reliability and validity, including a positive correlation with the Japanese version of the General and Risk Numeracy Questions (Lipkus-J) (r = .72, p < .001), supporting convergent validity with general numeracy. These findings provide initial evidence that the test may be useful for assessing health numeracy in Japanese adolescents, especially those with lower numeracy. However, the results should be interpreted within context. Although the survey was administered online in a supervised classroom setting, the web-based format may still introduce response bias, while the sample was drawn from a single Japanese private high school. In addition, measurement precision was highest in the lower ability range, which may limit sensitivity at higher levels of health numeracy.