Eaton et al. (2014). Toward a model-based approach to the clinical assessment of personality psychopathology.” – Article summary

Types refers to categories and traits refers to dimensions. In order to determine where an individual falls on a trait, the measure needs to measure the full range of the trait dimension. There are several models:

1. Latent trait model
   This model assumes that there is one or more underlying continuous distributions. There are no locations across the continuum that are unoccupied. The dimensional scores of this model can be changed to percentiles in order to facilitate interpretation.
2. Latent class model
   This model assumes a latent group ( class) structure for the distribution. There are a finite number of latent classes. They are mutually exclusive and nominal. It assumes conditional independence.
3. Hybrid model (factor mixture model)
   This model combines the continuous aspect of the latent trait model with the discrete aspects of the latent class model. This model assumes that there are classes, but there are individual differences in the classes. The distribution within a class is continuous.

Discrimination is a measure of how strongly the item taps into the latent trait. Conditional independence states that interitem correlations solely reflect class membership.