Latent variable model
|This article needs additional or better citations for verification. (April 2011) (Learn how and when to remove this template message)|
||This article includes a list of references, but its sources remain unclear because it has insufficient inline citations. (April 2011) (Learn how and when to remove this template message)|
It is assumed that the responses on the indicators or manifest variables are the result of an individual's position on the latent variable(s), and that the manifest variables have nothing in common after controlling for the latent variable (local independence).
Different types of the latent variable model can be grouped according to whether the manifest and latent variables are categorical or continuous: 
|Continuous||Factor analysis||Item response theory|
|Categorical||Latent profile analysis||Latent class analysis|
In factor analysis and latent trait analysis the latent variables are treated as continuous normally distributed variables, and in latent profile analysis and latent class analysis as from a multinomial distribution. The manifest variables in factor analysis and latent profile analysis are continuous and in most cases, their conditional distribution given the latent variables is assumed to be normal. In latent trait analysis and latent class analysis, the manifest variables are discrete. These variables could be dichotomous, ordinal or nominal variables. Their conditional distributions are assumed to be binomial or multinomial.
Because the distribution of a continuous latent variable can be approximated by a discrete distribution, the distinction between continuous and discrete variables turns out not to be fundamental at all. Therefore there may be a psychometrical latent variable, but not a psychological psychometric variable.