Psychometric Properties and Structures of the IAT, GPIUS and GAS Scales: A Bifactor Approach

Abstract

This study applied a bifactor approach to investigate the structures and simultaneously compare the psychometric properties of three popular self-report internet addiction (IA) instruments. A bifactor confirmatory factor analysis was used to address the structures of the three scales, while the bifactor multidimensional item response model was employed to compare the psychometric properties of the three scales. Results of bifactor confirmatory factor analysis (CFA) showed that the bifactor structures were suitable for the three scales. These corresponding bifactor structures were used in the subsequent bifactor multidimensional item response theory (MIRT) analysis. Results of the bifactor MIRT showed that: three instruments of IA performed well as a whole; the Generalised Problematic Internet Use Scale (GPIUS) and Internet Addiction Test (IAT) provided more test information and had less standard error of measurement, which ranged from −3 to −1 standard deviations of theta or IA severity; the Game Addiction Scale (GAS) performed better than the other two scales in that it can provide more test information in the large area of IA severity (from −1 to +3 SDs). These suggest that the GPIUS and IAT may be the best choice for epidemiological IA studies and for measuring those with lower IA severity. Meanwhile, the GAS may be a good choice when we recruit those with various levels of IA severity.