Identifiability of Latent Class Models with Covariates

Latent class models with covariates are widely used for psychological, social, and educational researches. Yet the fundamental identifiability issue of these models has not been fully addressed. Among the previous researches on the identifiability of latent class models containing covariates, Huang and Bandeen-Roche (2004, Psychometrika, 69:5-32) studied the local identifiability conditions. However, motivated by recent advances in the identifiability of restricted latent class models, particularly the Cognitive Diagnosis Models (CDMs), we show in this work that the conditions in Huang and Bandeen-Roche (2004) are only necessary but not sufficient to determine the local identifiability of the model parameters. To address the open identifiability issue for latent class models with covariates, this work establishes conditions to ensure the global identifiability of the model parameters in both strict and generic sense. Moreover, our results extend to polytomous-response CDMs with covariates, which generalizes the existing identifiability results for CDMs.