In reality, this model can be divided into three types of expansion. In research (a) The MM-IRT is expanded by creating the hierarchical class model (b) the multilevel latent class model (MLC) by Vermunt (2003, 2008a), which is expanded by adding characteristics at the bottom level, and (c) the MMIRT model by Vermunt (2008b) is expanded by adding the estimate of individual classes.