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See detailA note on weighted likelihood and Jeffreys modal estimation of proficiency levels in polytomous item response models
Magis, David ULg

in Psychometrika (in press)

Warm (1989) established the equivalence between the so-called Jeffreys modal and the weighted likelihood estimators of proficiency level with some dichotomous item response models. The purpose of this ... [more ▼]

Warm (1989) established the equivalence between the so-called Jeffreys modal and the weighted likelihood estimators of proficiency level with some dichotomous item response models. The purpose of this note is to extend this result to polytomous item response models. First, a general condition is derived to ensure the perfect equivalence between these two estimators. Second, it is shown that this condition is fulfilled by two broad classes of polytomous models including, among others, the partial credit, rating scale, graded response and nominal response models. [less ▲]

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See detailOn the relationships between Jeffreys modal and weighted likelihood estimation of ability under logistic IRT models
Magis, David ULg; Raîche, Gilles

in Psychometrika (2012), 77

This paper focuses on two estimators of ability with logistic item response theory models: the Bayesian modal (BM) estimator and the weighted likelihood (WL) estimator. For the BM estimator, Jeffreys’ ... [more ▼]

This paper focuses on two estimators of ability with logistic item response theory models: the Bayesian modal (BM) estimator and the weighted likelihood (WL) estimator. For the BM estimator, Jeffreys’ prior distribution is considered, and the corresponding estimator is referred to as the Jeffreys modal (JM) estimator. It is established that under the three-parameter logistic model, the JM estimator returns larger estimates than the WL estimator. Several implications of this result are outlined. [less ▲]

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See detailOptimization of blocked designs in fMRI studies
Maus, Bärbel ULg; van Breukelen, G. J. P.; Goebel, R. et al

in Psychometrika (2010), 75(2), 373390

Blocked designs in functional magnetic resonance imaging (fMRI) are useful to localize functional brain areas. A blocked design consists of different blocks of trials of the same stimulus type and is ... [more ▼]

Blocked designs in functional magnetic resonance imaging (fMRI) are useful to localize functional brain areas. A blocked design consists of different blocks of trials of the same stimulus type and is characterized by three factors: the length of blocks, i.e., number of trials per blocks, the ordering of task and rest blocks, and the time between trials within one block. Optimal design theory was applied to find the optimal combination of these three design factors. Furthermore, different error structures were used within a general linear model for the analysis of fMRI data, and the maximin criterion was applied to find designs which are robust against misspecification of model parameters. [less ▲]

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See detailAgreement between two independent groups of raters
Vanbelle, Sophie ULg; Albert, Adelin ULg

in Psychometrika (2009), 74

We propose a coefficient of agreement to assess the degree of concordance between two independent groups of raters classifying items on a nominal scale. This coefficient, defined on a population-based ... [more ▼]

We propose a coefficient of agreement to assess the degree of concordance between two independent groups of raters classifying items on a nominal scale. This coefficient, defined on a population-based model, extends the classical Cohen's kappa coefficient for quantifying agreement between two raters. Weighted and intraclass versions of the coefficient are also given and their sampling variance is determined by the Jackknife method. The method is illustrated on medical education data which motivated the research. [less ▲]

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