Mplus Users Guide v6.. - Muthén & Muthén

MODEL CommandCHAPTER 17MODEL COMMANDTHE Mplus FRAMEWORKIn this chapter, the MODEL command is discussed. The MODELcommand is used to describe the model to be estimated. The first part ofthis chapter describes the general modeling framework used by Mplusand introduces a set of terms that are used to describe the model to beestimated. The second part of this chapter explains how a model istranslated into the Mplus language using the options of the MODELcommand. The last part of the chapter describes variations of theMODEL command. The MODEL command has variations for use withmodels with indirect effects, models with linear and non-linearconstraints, models with parameter constraints for the Wald test,multiple group models, mixture models, multilevel models, and modelsfor generating data for Monte Carlo simulation studies.VARIABLESThere are three important distinctions that need to be made about thevariables in an analysis in order to be able to specify a model. Thedistinctions are whether variables are observed or latent, whethervariables are dependent or independent, and the scale of the observeddependent variables.OBSERVED OR LATENT VARIABLESTwo types of variables can be modeled: observed variables and latentvariables. Observed variables are variables that are directly measuredsuch as test scores and diagnostic criteria. They are sometimes referredto as manifest variables, outcomes, or indicators. Latent variables arevariables that are not directly measured such as ability, depression, andhealth status. They are measured indirectly by a set of observedvariables. There are two types of latent variables: continuous andcategorical. Continuous latent variables are sometimes referred to asfactors, dimension, constructs, or random effects. Categorical latentvariables are sometimes referred to as latent class variables or mixtures.567