Psychometric evaluation of the System Usability Scale in the context of a childrearing app co-designed for low- and middle-income countries.

Objective: The System Usability Scale (SUS) demonstrates good psychometric properties for a range of technologies; however, its reliability and factor structure in the context of a childrearing application (app) and variation across cultures remains largely unexplored. This study investigates the reliability and factor structure of the SUS in the context of a childrearing app that was co-designed for and implemented in diverse low- and middle-income countries (LMICs).

Methods: Parents and caregivers of children aged 0-5 years in five LMICs completed the SUS after having access to the app for a minimum of 2 and maximum of 24 weeks. Survey data from participants (668) was analysed using exploratory and confirmatory factor analysis methods.

Results: The bi-factor model shows the best fit to data (comparative fit index = 0.998; Tucker Lewis Index = 0.996; standardised root mean square residual = 0.033). Further analysis suggests that usability and learnability subscales provide additional information not contained in the total SUS score. A two-sample -test shows that younger caregivers, employed full- or part-time, and with fewer children reported significantly better app usability.

Conclusion: The SUS has good psychometric properties, and it is a valid and reliable tool for assessing the usability of mobile apps when used by parents and other caregivers for children's socioemotional and cognitive development. However, it is not essentially unidimensional and appears to have a multidimensional structure that could be specific to our context owing to variations in users' experience, culture, and language. The findings have implications for other mobile health interventions implemented in contexts with cultural and linguistic differences.