title: A Note on the Identifiability of Fixed-Effect 3PL Models.
abstract: In this note, we prove that the 3 parameter logistic model with fixed-effect abilities is identified only up to a linear transformation of the ability scale under mild regularity conditions, contrary to the claims in Theorem 2 of San Martín et al. (Psychometrika, 80(2):450-467, 2015a).
authors.affiliation: Department of Psychology, Boston College, 140 Commonwealth Ave, Chestnut Hill, MA, 02467 , USA. hao.wu.5@bc.edu.
authors.forename: Hao
authors.identifier: 0000-0001-6471-1774
authors.initials: H
authors.lastname: Wu
mesh_terms: D016015:Logistic Models; D015233:Models, Statistical; D008962:Models, Theoretical; D011594:Psychometrics
keywords: 3PL model; identification; item response theory