Personal profile
Research Interests
My current research concerns three lines of work:
(1) Combinatorial data analysis of individual differences based on multiple proximity matrices observed from different data sources (e.g., subjects, experimental conditions, time points);
(2) Large-scale nonmodel-based clustering, with particular focus on the p-median model;
(3) Cognitively Diagnostic Modeling
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Selected Publications:
Chiu, C.-Y., & Köhn, H. F. (2019). Consistency theory for the General NonParametric Classification Method. Psychometrika, 84, 830–845.
Köhn, H. F., & Chiu, C.-Y. (2019). Attribute hierarchy models in cognitive diagnosis: Identifiability of the latent attribute space and conditions for completeness of the Q-matrix. Journal of Classification, 36, 541–565
Köhn, H. F., & Chiu, C.-Y. (2018). How to build a complete Q-matrix for a cognitively diagnostic test. Journal of Classification, 35, 273–299.
Köhn, H. F. (2017). Citation classics commentary on Greenhouse and Geisser (1959): On methods in the analysis of profile data. Psychometrika, 82, 1209–1211.
Köhn, H. F., & Chiu, C.-Y. (2017). A procedure for assessing the completeness of the Q-matrices of cognitively diagnostic tests. Psychometrika, 82, 112–132.
Köhn, H. F., & Chiu, C.-Y. (2016). A proof of the duality of the DINA model and the DINO model. Journal of Classification, 33, 171-184.
Chiu, C.-Y., & Köhn, H. F. (2016). The Reduced RUM as a logit model: Parameterization and constraints. Psychometrika, 81, 350-370.
Chiu, C.-Y., & Köhn, H. F. (2016). Consistency of cluster analysis for cognitive diagnosis: The Reduced Reparameterized Unified Model and the General Diagnostic Model. Psychometrika, 81, 585-610.
Köhn, H. F., & Hubert, L. J. (2015). Hierarchical cluster analysis. Wiley StatsRef: Statistics Reference Online (WSR).
Köhn, H. F., Chiu, C.-Y., & Brusco, M. J. (2015). Heuristic cognitive diagnosis when the Q-matrix is unknown. British Journal of Mathematical and Statistical Psychology, 68, 268-291.
Köhn, H. F. (2011). A review of multiobjective programming and its application in quantitative psychology. Journal of Mathematical Psychology, 55, 386-396.
Köhn, H. F. (2010). Representation of individual differences in rectangular proximity data through anti-Q matrix decomposition. Computational Statistics and Data Analysis, 54, 2343-2357.
Köhn, H. F., Steinley, D., & Brusco, M. J. (2010). The p-median model as a tool for clustering psychological data. Psychological Methods, 15, 87-95.
Brusco, M. J., & Köhn, H. F. (2009). Clustering qualitative data based on binary equivalence relations: a variable neighborhood search procedure for the clique partitioning problem. Psychometrika, 74, 685-703.
Brusco, M. J., & Köhn, H. F. (2009). Exemplar-based clustering via simulated annealing: a comparison to affinity propagation and vertex substitution. Psychometrika, 74, 457-475.
Brusco, M. J., & Köhn, H. F. (2008). Optimal partitioning of a data set based on the p-median model. Psychometrika, 73, 89-105.
Brusco, M. J., & Köhn, H. F. (2008). Comment on “Clustering by passing messages between data points”. Science, 319, 726c.
Brusco, M. J., Köhn, H. F., & Stahl, S. (2008). Heuristic implementation of dynamic programming for matrix permutation problems in combinatorial data analysis. Psychometrika, 73, 503-522.
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A Two-Step Q-Matrix Estimation Method
Köhn, H. F., Chiu, C. Y., Oluwalana, O., Kim, H. & Wang, J., Mar 2025, In: Applied Psychological Measurement. 49, 1-2, p. 3-28 26 p.Research output: Contribution to journal › Article › peer-review
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Identifiability conditions in cognitive diagnosis: Implications for Q-matrix estimation algorithms
Kim, H., Köhn, H. F. & Chiu, C. Y., Dec 12 2025, (E-pub ahead of print) In: British Journal of Mathematical and Statistical Psychology.Research output: Contribution to journal › Article › peer-review
Open Access -
MCMC stopping rules in latent variable modelling
Kwon, S., Zhang, S., Köhn, H. F. & Zhang, B., Feb 2025, In: British Journal of Mathematical and Statistical Psychology. 78, 1, p. 225-257 33 p.Research output: Contribution to journal › Article › peer-review
Open Access -
Nonparametric CD-CAT for multiple-choice items: Item selection method and Q-optimality
Wang, Y., Chiu, C. Y. & Köhn, H. F., Feb 2025, In: British Journal of Mathematical and Statistical Psychology. 78, 1, p. 61-83 23 p.Research output: Contribution to journal › Article › peer-review
Open Access -
Plausible and Proper Multiple-Choice Items for Diagnostic Classification
Chiu, C. Y., Koehn, H. F. & Wang, Y., Dec 19 2025, (E-pub ahead of print) In: Psychometrika.Research output: Contribution to journal › Article › peer-review
Open Access