Behavior Genetics

, Volume 33, Issue 3, pp 271–278 | Cite as

A Model-Fitting Implementation of the DeFries-Fulker Model for Selected Twin Data

  • S. Purcell
  • P. C. Sham


In this research note, DeFries-Fulker (DF) regression analysis is reframed in model-fitting terms, where an individual's expected score is modeled as a function of their co-twin's proband status. This more flexible implementation of the DF model allows DZ-O twins to be incorporated in a sex-limitation model. Brief simulation results are presented along with the Mx scripts used.

Twins DeFries-Fulker analysis sex differences maximum likelihood estimation 


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Copyright information

© Plenum Publishing Corporation 2003

Authors and Affiliations

  • S. Purcell
  • P. C. Sham

There are no affiliations available

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