Koopman, L., Zijlstra, B. J., & Van der Ark, L. A. (2025). Assumptions and Properties of Two-Level Nonparametric Item Response Theory Models. Psychometrika, 90(1), 208-28. https://doi.org/10.1017/psy.2024.9
Koopman, L. & Braeken, J. (2024). Investigating the Ordering Structure of Clustered Items Using Nonparametric Item Response Theory. Educational and Psychological Methods, 85(2), 336-356. https://doi.org/10.1177/00131644241274122
Koopman, L., Zijlstra, B. J., & Van der Ark, L. A. (2023). Evaluating model fit in two-level Mokken scale analysis. Psych, 5(3), 847-865. https://doi.org/10.3390/psych5030056
Van der Ark, L. A., Bergsma, W. P., & Koopman, L. (2023). Maximum augmented emperical likelihood estimation of categorical marginal models for large sparse contingency tables. Psychometrika, 38(4), https://doi.org/10.1007/s11336-023-09932-7
Koopman, L., Zijlstra, B. J. H., & Van der Ark, L. A. (2022). A two-step, test-guided Mokken scale analysis, for nonclustered and clustered data. Quality of Life Research, 31, 25-36. http://doi.org/10.1007/s11136-021-02840-2
Koopman, L., Zijlstra, B. J. H., & Van der Ark, L. A. (2020). Standard errors of two-level scalability coefficients. British Journal of Mathematical and Statistical Psychology, 73, 213-236. http://doi.org/10.1111/bmsp.12174
Koopman, L., Zijlstra, B. J. H., De Rooij, M., & Van der Ark, L. A. (2020). Bias of two-level scalability coefficients and their standard errors. Applied Psychological Measurement, 44(3), 197-214. http://doi.org/10.1177/0146621619843821
Fukkink, R., Jilink, L., Op den Kelder, R., Zeijlmans, K., Bollen, I., Koopman, L. (2019). The development of interaction skills in preservice teacher education: A mixed-methods study of Dutch pre-service teachers. Early Childhood Education Journal, 47, 321–329. https://doi.org/10.1007/s10643-019-00927-7
Book:
Koopman, L. (2022). Nonparametric item response theory for multilevel test data. https://dare.uva.nl/search?identifier=7982e65d-3c1b-4f9a-af32-686d5591068e
Book chapters:
Sijtsma, K. & Koopman, L. & Van der Ark, L.A. (2025). Nonparametric item response theory and Mokken scale analysis. Advance online publication. https://doi.org/10.1016/B978-0-443-26629-4.00106-4
Koopman L. (2023). Effect of within-group dependency on fit statistics in Mokken scale analysis in the presence of two-level test data. In: Wiberg M., Molenaar D., González J., Kim J. S., & Hwang, H. (Eds), Quantitative Psychology – The 87th Annual Meeting of the Psychometric Society, Bologna, Italy, 2022. Springer. https://doi.org/10.1007/978-3-030-74772-5_16
Koopman L., Zijlstra B. J. H., van der Ark L. A. (2021). Range-preserving confidence intervals and significance tests for scalability coefficients in Mokken scale analysis. In: Wiberg M., Molenaar D., González J., Böckenholt U., Kim J. S. (Eds), Quantitative Psychology: The 85th Annual Meeting of the Psychometric Society, Virtual, 2020 (pp. 175 – 185). Switserland: Springer. https://doi.org/10.1007/978-3-030-74772-5_16
Van der Ark, L. A., Korf, W., Peters, P., Chen, M., Ten Hove, D., & Koopman, L. (2019). Onderzoek naar de verbetering van tests en vragenlijsten voor de pedagogische praktijk [Research into the Improvement of Tests and Questionnaires]. In L. Houweling, H. Viëtor, H. de Deckere, & W. de Jong (Eds.), De belofte van de jeugd?! Pedagogiek in de 21e eeuw (pp. 81 – 92). Amsterdam, The Netherlands: SWP
Koopman, L., Zijlstra, B. J. H., & Van der Ark, L. A. (2017). Weighted Guttman errors: Handling ties and two-level data. In L. A. Van der Ark, M. Wiberg, S. A. Culpepper, J. A. Douglas, & W.-C. Wang (Eds.), Quantitative psychology: The 81st annual meeting of the Psychometric Society, Asheville, North Carolina, 2016 (pp. 183 – 190). New York, NY: Springer. https://doi.org/10.1007/978-3-319-56294-0.17
Reports:
Koopman, L., Oort, F. J., & Klaassen, C. A. J. (2017) Evaluating the scientific veracity of PhD theses written under supervision of prof. dr. Jens Förster. Retrieved from http://www.uva.nl/binaries/content/assets/ uva/nl/persvoorlichting/actueel/veracityanalysisphds.pdf?3026353542960
Software:
Co-author to R-package mokken. https://cran.r-project.org/web/packages/mokken/index.html.
Manuscripts submitted for publication
Lortz S. A. J., Post, W. J., Koopman, L., Paap M. C. S. (2025). Stability and Scalability in Mokken Scale Analysis in the Presence of Small Samples and Deviant Items with Dichotomous Response Data.
Manuscripts in preparation:
Koopman, L., Ten Hove, D., & De Haan, R. (2024). Investigating multilevel interrater reliability in the presence of a planned missing data design, with an application to the Dutch HoNOS+ questionnaire.
Ten Hove, D. & Koopman, L. (2024). A Tutorial on Estimating Interrater Reliability from Incomplete and Dependent Data.
Van der Ark, L. A., Zijlstra, B. J. H., & Koopman, L. (2024). A tutorial on how to do a Mokken scale analysis on two-level test data.
PROFESSIONAL REPRESENTATION
Koopman, L. & Braeken, J. (2024, July 16-19). Investigating the Ordering Structure of Clustered Items [oral presentation]. International Meeting of the Psychometric Society, Prague, Czech Republic
Koopman, L. & Braeken, J. (2023, September 5-7). Investigating the Ordering Structure of Clustered Items [oral presentation]. Frontier Research in Educational Measurement FREMO2023, Oslo, Norway
Koopman, L. (2023, August 29). Investigating the Ordering Structure of Clustered Items [invited speaker for Brown bag seminar at the Centre for Educational Measurement at the University of Oslo]. Oslo, Norway
Koopman, L., Zijlstra, B. J. H., & Van der Ark, L. A. (2022, July 12-15). Two-level nonparametric item response theory models: Assumptions and ordering properties [oral presentation]. International Meeting of the Psychometric Society, Bologna, Italy
Koopman, L. Zijlstra, B. J. H., & Van der Ark, L. A. (2021, December 9). Mokken scale analysis for two-level test data [oral presentation]. 31th IOPS Winter Conference, Virtual Meeting
Koopman, L., Zijlstra, B. J. H., & Van der Ark, L. A. (2021, July 21-23). A two-step procedure for scaling multilevel data using Mokken’s scalability coefficients [oral presentation]. 9th European Congress of Methodology, Virtual Meeting
Koopman, L. (2021, January 21). UvA FMG conference Social and Behavioural Data Science Center [facilitator break-out session ‘Research: analysis and computational methods’]. Virtual Meeting
Koopman, L., Zijlstra, B. J. H., & Van der Ark, L. A. (2020, July 13-17). Invited address: New advances in Mokken scale analysis [Spotlight Talk, pre-recorded oral presentation and live session during the meeting]. International Meeting of the Psychometric Society, Virtual Meeting
Koopman, L., Zijlstra, B. J. H., & Van der Ark, L. A. (2020, February 27-28). Mokken’s Scalability Coefficients for Multilevel Data [oral presentation]. Psychoco International Workshop on Psychometric Computing, Dortmund, Germany
Koopman, L., Zijlstra, B. J. H., & Van der Ark, L. A. (2018, June 14-15). Checking Assumptions in Two-Level Mokken Scale Analysis [poster presentation]. 33rd IOPS Summer Conference, Amsterdam, The Netherlands
Koopman, L., Zijlstra, B. J. H., & Van der Ark, L. A. (2018, July 25-27). Checking Assumptions in Two-Level Mokken Scale Analysis [invited speaker for symposium: New Developments in Mokken Scale Analysis]. 8th European Congress of Methodology, Jena, Germany
Van der Ark, L. A., Chen, M., Koopman, L., Korf, W., Peters, P., & Ten Hove, D. (2017, September 22). De Belofte van de Onderzoekende Jeugd [The Promise of the Researching Youth, oral presentation]. Vereniging tot Bevordering van de Studie der Pedagogiek congres, Garderen, The Netherlands
Koopman, L., Zijlstra, B. J. H., & Van der Ark, L. A. (2017, July 18-21). Bias of Two-Level Scalability Coefficients and Their Standard Errors [oral presentation]. International Meeting of the Psychometric Society, Zurich, Switserland
SERVICES
Ad hoc reviewer
- Multiple journals, e.g., Educational and Psychological Measurement; Testing, Psychometrics, Methodology in Applied Psychology; Quality of Life Research
- Book: Mokken scale analysis in language assessment
- IOPS: PhD research proposals
GRANTS AND AWARDS
NRO 2025 Kansrijke aanpakken: parels uit de praktijk – fase 1: 20743. (Nationaal Regieorgaan Onderwijsonderzoek). Costs for research project: Vertrouwen en verbinding: Maatwerkaanpak voor Thuiszitters
Gustafsson-Skrondal Visiting Scholarship 2022-2023: Nine months’ salary, research costs, moving costs for research project Progressive Psychometrics: Validating, Starting, Stopping, and Scoring Adaptive Progressive Tests.
NWO Research Talent Grant 2016: 406.16.554 (Netherlands Organisation for Scientific Research). Salary and research costs for PhD project: Scaling methods for multilevel test data.
Research Priority Area Yield Graduate Programme (University of Amsterdam).
Salary and research costs for PhD project: Scaling methods for multilevel test data. Declined in favor of the NWO Research Talent Grant.
Stichting Kohnstamm Fonds voor Onderwijsresearch granted € 428,- for conference visit EAM 2018 (Jena, Germany)
Stichting Kohnstamm Fonds voor Onderwijsresearch granted € 116,- for conference visit IMPS 2017 (Zurich, Switserland)
Best thesis of the year award 2016-2017 of the department of Child Development and Education at the University of Amsterdam (thesis Standard errors for two-level scalability coefficients)