Don't Tie Yourself to an Onion: Don’t Tie Yourself to Assumptions of Normality

Maarten Marsman, Gunter Maris, Timo Bechger

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A structural measurement model (Adams, Wilson, & Wu, 1997) consists of an item response theory model for responses conditional on ability and a structural model that describes the distribution of ability in the population. As a rule, ability is assumed to be normally distributed in the population. However, there are situations where there is reason to assume that the distribution of ability is nonnormal. In this paper, we show that nonnormal ability distributions are easily modeled in a Bayesian framework
Original languageUndefined
Title of host publicationPsychometrics in practice at RCEC
EditorsTheodorus Johannes Hendrikus Maria Eggen, Bernard P. Veldkamp
ISBN (Print)9789036533744
Publication statusPublished - 2012

Publication series



  • Item Response Theory
  • one-parameter logistic model
  • finite mixture
  • Markov chain Monte Carlo
  • plausible values
  • IR-80205
  • Bayes estimates
  • Gibbs sampler

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