Latent variable models involve restrictions on the data that can be formulated in terms of "misspecifications": restrictions with a model-based meaning. Examples include zero cross-loadings and local dependencies, as well as “measurement invariance” or “differential item functioning”. If incorrect, misspecifications can potentially disturb the main purpose of the latent variable analysis—seriously so in some cases.
Recently, I proposed to evaluate whether a particular analysis at hand is such a case or not.
To do this, I define a measure based on the likelihood of the restricted model that approximates the change in the parameters of interest if the misspecification were freed, the EPC-interest. The main idea is to examine the EPC-interest and free those misspecifications that are “important” while ignoring those that are not. I have implemented the EPC-interest in the lavaan software for structural equation modeling and the Latent Gold software for latent class analysis.
This approach can resolve several problems and inconsistencies in the current practice of model fit evaluation used in latent variable analysis, something I illustrate using analyses from the “measurement invariance” literature and from item response theory.