Random Intercept Item Factor Analysis

(WP 02/03 Clave pdf) The common factor model assumes a linear relation between the observed variables and a set of underlying latent traits. It also assumes that the linear coefficients, intercepts and slopes (factor loadings), linking the observed variables to the latent traits are fixed coefficients (i.e., common for all subjects). We partially relax the fixed coefficients assumption by letting the intercepts in the factor model change across subjects while keeping the factor loadings fixed.