, Volume 62, Issue 4, pp 471–493 | Cite as

Departure from normal assumptions: A promise for future psychometrics with substantive mathematical modeling

  • Fumiko Samejima


Normal assumptions have been used in many psychometric methods, to the extent that most researchers do not even question their adequacy. With the rapid advancement of computer technologies in recent years, psychometrics has extended its territory to include intensive cognitive diagnosis, etcetera, and substantive mathematical modeling ha become essential. As a natural consequence, it is time to consider departure from normal assumptions seriously. As examples of models which are not based on normality or its approximation, the logistic positive exponent family of models is discussed. These models include the item task complexity as the third parameter, which determines the single principle of ordering individuals on the ability scale.

Key words

latent trait models item response theory substantive mathematical modeling logistic positive exponent family of models task complexity dichotomous responses 


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Copyright information

© The Psychometric Society 1997

Authors and Affiliations

  • Fumiko Samejima
    • 1
  1. 1.Psychology DepartmentUniversity of TennesseeKnoxville

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