Examining the hierarchical factor structure of the SF-36 Taiwan version by exploratory and confirmatory factor analysis

Rationale:  The purpose of this study was to examine the factor structure of the Medical Outcome Study Short Form-36 Taiwan version (SF-36 Taiwan version) using data from the 2001 National Health Interview Survey in Taiwan. Method:  The 2001 National Health Interview Survey was conducted by stratified multistage systematic sampling, resulting in 19 777 valid responses for the SF-36 Taiwan version. In this study, the 19 777 participants were randomly divided into two independent samples. One sample (n = 9856) was used for exploratory factor analysis (EFA), and the other (n = 9921) was used for confirmatory factor analysis (CFA). Results:  The EFA suggested a seven-first-order-factor structure for the SF-36 Taiwan version. In addition, hierarchical EFA revealed that there was only one second-order factor underlying the seven first-order factors. Further, CFA was conducted on the other sample to compare the performances of the original model with eight first-order factors and two second-order factors, and the revised model with seven first-order factors and one second-order factor. The CFA results revealed that the original model was better than the revised model. Conclusion:  According to the EFA and CFA, it can be concluded that the original structure is still acceptable for the SF-36 Taiwan version.