Evaluation of Validity and Reliability of the Eight-Item Body Shape Questionnaire (BSQ-8C) Indonesian Version: Mixture Rasch Model Approach

This research aims to evaluate and validate the eight-item Body Shape Questionnaire (BSQ-8C) instrument in Indonesian using the Rasch model and mixture Rasch model approaches with 408 respondents. The analysis showed that the instrument was unidimensional (eigenvalue 12.5; 60.9 percent), with high reliability (person reliability .85; item reliability .99). The rating scale functioned well, with the Andrich threshold increasing regularly (-1.21 to 1.47). The item fit analysis showed measure values from -.63 to .73 and PT-Measure Corr from .68 to .77. The Wright map indicated an adequate distribution of respondents’ abilities, while differential item functioning analysis showed no significant bias based on gender. The mixture Rasch model results identified two latent classes, reflecting diverse response patterns, and supported the two-class model as the best, based on the decrease in AIC, BIC, and CAIC values. Overall, the Indonesian version of the BSQ-8C showed good validity and reliability in measuring body shape perception among the Indonesian population. The results of the Rasch model analysis showed that the scale implications of this instrument tended to measure respondents with moderate levels of agreement, suggesting that improvements were needed on certain items.