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- Matthijs J. Warrens
- Adv. Data Analysis and Classification
- 2010

In a validity study a dichotomous variable Y is often compared to a ‘gold standard’ variable X. For example, in a medical test evaluation one has a ‘gold standard’ evaluation of the presence/absence or type of a disease against which a test is assessed. A 2× 2 study can be summarized in a table like Table 1 (Warrens, 2008a, 2008b, 2009). In Table 1, the… (More)

- Matthijs J. Warrens
- J. Classification
- 2010

Suppose two judges each classify a group of objects into one of several nominal categories. It has been observed in the literature that, for fixed observed agreement between the judges, Cohen’s kappa penalizes judges with similar marginals compared to judges who produce different marginals. This paper presents a formal proof of this phenomenon.

- Matthijs J. Warrens
- J. Classification
- 2008

It is shown that one can calculate the Hubert-Arabie adjusted Rand index by first forming the fourfold contingency table counting the number of pairs of objects that were placed in the same cluster in both partitions, in the same cluster in one partition but in different clusters in the other partition, and in different clusters in both, and then computing… (More)

- Matthijs J. Warrens
- The British journal of mathematical and…
- 2011

Cohen's kappa is presently a standard tool for the analysis of agreement in a 2 × 2 reliability study, and weighted kappa is a standard statistic for summarizing a 2 × 2 validity study. The special cases of weighted kappa, for example Cohen's kappa, are chance-corrected measures of association. For various measures of 2 × 2 association it has been observed… (More)

- Lorenza S. Colzato, Matthijs J. Warrens, Bernhard Hommel
- Quarterly journal of experimental psychology
- 2006

Individual performance was compared across three different tasks that tap into the binding of stimulus features in perception, the binding of action features in action planning, and the emergence of stimulus-response bindings ("event files"). Within a task correlations between the size of binding effects were found within visual perception (e.g., the… (More)

- Matthijs J. Warrens
- Psychometrika
- 2008

This paper studies correction for chance in coefficients that are linear functions of the observed proportion of agreement. The paper unifies and extends various results on correction for chance in the literature. A specific class of coefficients is used to illustrate the results derived in this paper. Coefficients in this class, e.g. the simple matching… (More)

Cohen’s weighted kappa is a popular descriptive statistic for measuring the agreement between two raters on an ordinal scale. Popular weights for weighted kappa are the linear weights and the quadratic weights. It has been frequently observed in the literature that the value of the quadratically weighted kappa is higher than the value of the linearly… (More)

- Matthijs J. Warrens
- Psychometrika
- 2008

We discuss properties that association coefficients may have in general, e.g., zero value under statistical independence, and we examine coefficients for 2 × 2 tables with respect to these properties. Furthermore, we study a family of coefficients that are linear transformations of the observed proportion of agreement given the marginal probabilities. This… (More)

- Matthijs J. Warrens
- Adv. Data Analysis and Classification
- 2012

An agreement table with n ∈N≥3 ordered categories can be collapsed into n−1 distinct 2×2 tables by combining adjacent categories. Vanbelle and Albert (Stat. Methodol. 6:157–163, 2009c) showed that the components of Cohen’s weighted kappa with linear weights can be obtained from these n−1 collapsed 2× 2 tables. In this paper we consider several consequences… (More)