Psychometric Analysis of the SF-12 Health Survey in Korean American Adults
Background:The SF-12 is a widely used measure of perceived health status. Despite reports of reliability and validity, prior studies found a poor model fit using the instrument with some ethnic populations.
Methods: The parent study collected data from a convenience sample of 517 Korean American adults through the Korean community in a Midwestern city using survey questionnaires. Participants completed the survey in either Korean (n=256) or English (n=261). Measurement theory guided the current study. This data analysis focused on the SF-12 health survey and examined reliability and validity using internal consistency test and confirmatory factor analysis.
Results: The sample was 57.1% female with mean age 41.6 ± 13.40, and 78.4% college educated. Compared to national norms, the sample was healthy based on the physical health scores (47.9 ± 7.9 in the Korean survey sample and 50.2 ± 8.3 in the English survey sample) and mental health scores (47.3 ± 8.6 in the Korean survey sample; 49.5 ± 9.8 in the English survey sample). Reliability was supported with Cronbach’s alphas (.81-.83 for physical health and .82-.84 for mental health). Confirmatory factor analysis showed that physical and mental health are highly correlated to each other (r = .79 for the Korean survey sample; r = .73 for the English survey sample) at p <.05. All items loaded significantly on their respective construct with good factor loadings (r>.60) except two items (self-rated health and have a lot of energy), which was consistent with previous research findings. The measurement models of the SF-12 demonstrated an acceptable fit to the data according to fit indices: RMSEA (<.08), NFI, NNFI, and CFI (all >.90) in the sample of the Korean and English surveys.
Implications: This study demonstrated evidence of reliability and validity in a healthy Korean American adult sample. Additional study in more diverse populations is recommended to evaluate the validity of the measure, in particular, for the two items that cross loaded on physical and mental health.