The personal well-being index-school children (PWI-SC) is designed as a cross-cultural instrument to measure subjective well-being among high school-aged children. Several published cross-cultural studies have confirmed adequate psychometric performance in terms of reliability, validity, and measurement invariance. This study adds to this literature by applying the Rasch approach to estimate invariant comparison in a cross-cultural context, applied to both Australian and Portuguese high school students. Participants were an age- and gender-matched convenience sample of 1,040 adolescents (520 cases in each group, 51.54% male) who ranged in age from 12 to 18 years (M = 14.25 years, SD = 1.71 years). It is found that both Portuguese and Australian data fit the Rasch measurement model, with excellent levels of reliability at a country level. However, when all of the data were combined, a slight misfit was found. This was resolved by removing some issues with item thresholds in standard of living among the Australian data and splitting the data by country on health. This allowed both Australian and Portuguese cases to differ on the health item. We conclude that the PWI-SC is unidimensional, with some evidence of mild, but acceptable local dependency. This study further supports the cross-cultural validity of the PWI-SC and the use of this measure in the Australian and Portuguese context but also indicates a potential direction that development of the PWI-SC might proceed.
Keywords: Rasch analysis; adolescents; personal well-being index; school children; subjective well-being.