dr. V.E.C. (Letty) Koopman

Assistant Professor

Faculty of Behavioural and Social Sciences

Telephone:

+31 50 36 36540

E-mail:

l.koopman rug.nl

ORCID Research Portal

Publications

Assumptions and Properties of Two-Level Nonparametric Item Response Theory Models

Koopman, L., Zijlstra, B. J. H. & van der Ark, L. A., Mar-2025, In: Psychometrika. 90, 1, p. 208-228 21 p.

Research output: Contribution to journal › Article › Academic › peer-review

Investigating the Ordering Structure of Clustered Items Using Nonparametric Item Response Theory

Koopman, L. & Braeken, J., Apr-2025, In: Educational and Psychological Measurement. 85, 2, p. 336-356 21 p.

Research output: Contribution to journal › Article › Academic › peer-review

Effect of Within-Group Dependency on Fit Statistics in Mokken Scale Analysis in the Presence of Two-Level Test Data

Koopman, L., 2023, Quantitative Psychology: The 87th Annual Meeting of the Psychometric Society, Bologna, Italy, 2022. Wiberg, M., Molenaar, D., González, J., Kim, J.-S. & Hwang, H. (eds.). Springer, p. 221-232 12 p. (Springer Proceedings in Mathematics & Statistics; vol. 422).

Research output: Chapter in Book/Report/Conference proceeding › Chapter › Academic › peer-review

Evaluating Model Fit in Two-Level Mokken Scale Analysis

Koopman, L., Zijlstra, B. J. H. & der Ark, L. A. V., 7-Aug-2023, In: Psych. 5, 3, p. 847-865 19 p.

Research output: Contribution to journal › Article › Academic › peer-review

Maximum Augmented Empirical Likelihood Estimation of Categorical Marginal Models for Large Sparse Contingency Tables

van der Ark, L. A., Bergsma, W. P. & Koopman, L., Dec-2023, In: Psychometrika. 88, p. 1228-1248 21 p.

Research output: Contribution to journal › Article › Academic › peer-review

A two-step procedure for scaling multilevel data using Mokken's scalability coefficients

Koopman, L., Zijlstra, B. J. H. & van der Ark, L. A., 2022.

Research output: Contribution to conference › Paper › Academic

A two-step, test-guided Mokken scale analysis, for nonclustered and clustered data

Koopman, L., Zijlstra, B. J. H. & van der Ark, L. A., 2022, In: Quality of Life Research. 31, p. 25-36 12 p.

Research output: Contribution to journal › Article › Academic › peer-review

Nonparametric item response theory for multilevel test data

Koopman, L., 3-Nov-2022, 156 p.

Research output: Thesis › Thesis fully external

Range-Preserving Confidence Intervals and Significance Tests for Scalability Coefficients in Mokken Scale Analysis

Koopman, L., Zijlstra, B. J. H. & van der Ark, L. A., 2021, Quantitative Psychology: The 85th Annual Meeting of the Psychometric Society, Virtual. Wiberg, M., Molenaar, D., González, J., Böckenholt, U. & Kim, J.-S. (eds.). Springer, p. 175-185 11 p. (Springer Proceedings in Mathematics & Statistics; vol. 353).

Research output: Chapter in Book/Report/Conference proceeding › Chapter › Academic › peer-review

Bias of Two-Level Scalability Coefficients and Their Standard Errors

Koopman, L., Zijlstra, B. J. H., de Rooij, M. & van der Ark, L. A., 14-May-2020, In: Applied Psychological Measurement. 44, 3, p. 197-214 18 p.

Research output: Contribution to journal › Article › Academic › peer-review

All (16) publications

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