Fitting the Reduced RUM with Mplus: A Tutorial

Chia Yi Chiu, Hans Friedrich Köhn, Huey Min Wu

Research output: Contribution to journalArticlepeer-review


The Reduced Reparameterized Unified Model (Reduced RUM) is a diagnostic classification model for educational assessment that has received considerable attention among psychometricians. However, the computational options for researchers and practitioners who wish to use the Reduced RUM in their work, but do not feel comfortable writing their own code, are still rather limited. One option is to use a commercial software package that offers an implementation of the expectation maximization (EM) algorithm for fitting (constrained) latent class models like Latent GOLD or Mplus. But using a latent class analysis routine as a vehicle for fitting the Reduced RUM requires that it be re-expressed as a logit model, with constraints imposed on the parameters of the logistic function. This tutorial demonstrates how to implement marginal maximum likelihood estimation using the EM algorithm in Mplus for fitting the Reduced RUM.

Original languageEnglish (US)
Pages (from-to)331-351
Number of pages21
JournalInternational Journal of Testing
Issue number4
StatePublished - Oct 1 2016


  • LCDM
  • MCMC
  • Mplus
  • cognitive diagnosis
  • diagnostic models
  • general cognitive
  • reduced RUM EM

ASJC Scopus subject areas

  • Social Psychology
  • Education
  • Modeling and Simulation


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