Time invariance of three ultra-brief internet-related instruments: Smartphone Application-Based Addiction Scale (SABAS), Bergen Social Media Addiction Scale (BSMAS), and the nine-item Internet Gaming Disorder Scale- Short Form (IGDS-SF9) (Study Part B).

Given the many technological advances over the past two decades, a small minority of young people are at risk of problematic use or becoming addicted to these technologies (including activities on the internet and smartphones). Many brief psychometric scales have been developed to assess those at risk of problematic use or addiction including the six-item Smartphone Application-Based Addiction Scale [SABAS], the six-item Bergen Social Media Addiction Scale [BSMAS], and the nine-item Internet Gaming Disorder Scale-Short Form [IGDS-SF9]). However, to date, the reproducibility of these three scales has only been examined over a short period of time (e.g., two weeks), and it is unclear whether they are time invariant across a longer period (e.g., three months). Given the emergence of internet and smartphone addiction in Chinese population, the present study translated the three instruments into Chinese and recruited 640 university students (304 from Hong Kong [99 males] and 336 from Taiwan [167 males]) to complete the three scales twice (baseline and three months after baseline). Multigroup confirmatory factor analysis (MGCFA) was applied to examine the time invariance. The intraclass correlation coefficient (ICC) was used to assess the relative reliability, and the percentage of smallest real difference (SRD%) was utilized to explore the absolute reliability for the three scales. MGCFA showed that all three scales were time invariant across three months. ICC demonstrated that all the scales were satisfactory in reproducibility (0.82 to 0.94), and SRD% indicated that all the scales had acceptable measurement noise (23.8 to 29.4). In conclusion, the short, valid, reliable, and easy-to-use Chinese SABAS, BSMAS, and IGDS-SF9 show good properties across periods of three months.