All analyses were conducted in Mplus (Muthén & Muthén, 1998–2007). IRT models were derived from a single-factor model, with latent trait group means set to 0, latent variances set to 1, and scale factors set to 1, using the program-default weighted least squares estimator (WLSMV). Parameter estimates were made using a two-parameter logistic IRT model and were calculated directly from factor parameters (Muthén & Asparouhov, 2002).
