Testing unidimensionality in polytomous Rasch models

A fundamental assumption of most IRT models is that items measure the same unidimensional latent construct. For the polytomous Rasch model two ways of testing this assumption against specific multidimensional alternatives are discussed. One, a marginal approach assuming a multidimensional parametric latent variable distribution, and, two, a conditional approach with no distributional assumptions about the latent variable. The second approach generalizes the Martin-Löf test for the dichotomous Rasch model in two ways: to polytomous items and to a test against an alternative that may have more than two dimensions. A study on occupational health is used to motivate and illustrate the methods.The authors would like to thank Niels Keiding, Klaus Larsen and the anonymous reviewers for valuable comments to a previous version of this paper. This research was supported by a grant from the Danish Research Academy and by a general research grant from Quality Metric, Inc.     

Making Connections: Categorisations and Particularisations in Students’ Literary Argument

This article investigates how students reason and argue to make sense of fictional literature. Excerpts from students’ talk are analysed using the concepts categorisation, particularisation and recontextualisation, and interpreted from a socio-cultural, dialogical perspective. The analyses show that the students’ arguments oscillate between personal experience and the novel, and between categorising and particularising perspectives. The subject relevance of talk that lies between everyday and scientific talk, and between personal and analytic readings, is revealed. The bridging of different readings, different language practices, and different learning contexts is discussed.     

On For Someone’s Sake Attitudes

Personal value, i.e., what is valuable for us (rather than value simpliciter), has recently been analysed in terms of so-called for-someone’s-sake attitudes. This paper is an attempt to add flesh to the bone of these attitudes that have not yet been properly analysed in the philosophical literature. By employing a distinction between justifiers and identifiers, which corresponds to two roles a property may play in the intentional content of an attitude, two different kinds of for-someone’s-sake attitudes can be identified. Moreover, it is argued that one of these kinds is particularly difficult to include in an analysis of value simpliciter but not in an analysis of value for.     

What is it for a Life to go Well (or Badly)?: Some Critical Comments on Wayne Sumner’s Theory of Welfare

In an effort to construct a plausible theory of experience-based welfare, Wayne Sumner imposes two requirements on the relevant kind of experience: the information requirement and the autonomy requirement. I argue that both requirements are problematic. First, I argue (very briefly) that a well-know case like ‘the deceived businessman’ need not support the information requirement as Sumner believes. Second, I introduce a case designed to cast further doubt on the information requirement. Third, I attend to a shortcoming in Sumner’s theory of welfare, namely that it is unclear which of later and informed assessments are to be treated as authoritative when it comes to the evaluation of a person’s welfare. Finally, I suggest that, in combination with ‘welfarism’ (to which Sumner subscribes, and which has it that welfare is all that matters from a moral viewpoint), the information requirement entail morally troublesome conclusions: e.g. the conclusion that, from a moral point of view, we should, other things being equal, only to be concerned with the alternative that makes one person slightly better off in respect of welfare instead of also being morally concerned with the alternative that makes one person very happy.     

Regular Minimality and Thurstonian-type modeling

A Thurstonian-type model for pairwise comparisons is any model in which the response (e.g., “they are the same” or “they are different”) to two stimuli being compared depends, deterministically or probabilistically, on the realizations of two randomly varying representations (perceptual images) of these stimuli. The two perceptual images in such a model may be stochastically interdependent but each has to be selectively dependent on its stimulus. It has been previously shown that all possible discrimination probability functions for same–different comparisons can be generated by Thurstonian-type models of the simplest variety, with independent percepts and deterministic decision rules. It has also been shown, however, that a broad class of Thurstonian-type models, called “well-behaved” (and including, e.g., models with multivariate normal perceptual representations whose parameters are smooth functions of stimuli) cannot simultaneously account for two empirically plausible properties of same–different comparisons, Regular Minimality (which essentially says that “being least discriminable from” is a symmetric relation) and nonconstancy of the minima of discrimination probabilities (the fact that different pairs of least discriminable stimuli are discriminated with different probabilities). These results have been obtained for stimulus spaces represented by regions of Euclidean spaces. In this paper, the impossibility for well-behaved Thurstonian-type models to simultaneously account for Regular Minimality and nonconstancy of minima is established for a much broader notion of well-behavedness applied to a much broader class of stimulus spaces (any Hausdorff arc-connected ones). The universality of Thurstonian-type models with independent perceptual images and deterministic decision rules is shown (by a simpler proof than before) to hold for arbitrary stimulus spaces.     

Educational Practice and Development of Human Capabilities

When you enrol as a student you are assigned a ‘place’ in education. This assignment will gradually imply an assessment of you as a human being. We argue that these are processes taking place in educational practice. In our orientation in educational research an orientation towards a theory of action has been inspired by the French philosopher Paul Ricoeur. In our search for an educational practice that could describe what it is that makes the student a capable human being we continue in the spirit of Ricoeur. The text is divided in two parts. In the first part, Basic Capabilities in Education, we are asking: Who is the student if education is the process where the student learns to be a capable human being? We try to answer this with the help of Ricoeur’s phenomenology of the capable human being which is structured around the capacity to speak, to act, to tell and finally to impute. In the second part, Institutional Mediations of Capabilities in Education, we try to show how the transmission of the human capacities to an actualization through education at an institutional level, represented by the teacher, is necessary. If the student shall become a capable human being s/he has to have conditions for actualizations of her capacities. A paradigm for this is found in the process of assigning and assessing in education.     

From origami to software development: a review of studies on judgment-based predictions of performance time

This article provides an integrative review of the literature on judgment-based predictions of performance time, often described as task duration predictions in psychology and as expert-based effort estimation in engineering and management science. We summarize results on the characteristics of performance time predictions, processes and strategies, the influence of task characteristics and contextual factors, and the relations between estimates and characteristics of the estimator. Although dependent on the type of study and the level of analysis, underestimation was more frequently reported than overestimation in studies from the engineering and management literature. However, this was not the case in studies from the psychology literature. Our summaries challenge earlier results regarding the effects of factors such as complexity/difficulty and experience. We also question the recurrent finding that small tasks are overestimated and large tasks are underestimated, as this to some extent can be a statistical artifact caused by random error. Several other influences on predictions are identified and discussed. These include various types of anchoring effects, performance and accuracy incentives, task decomposition, request formats, group estimation, revisions of initial ideal or incomplete estimates, level of abstraction, and superficial cues. We summarize similarities and differences between performance time predictions (e.g., number of work hours) and completion time predictions (e.g., delivery dates) because many studies fail to distinguish between these 2 types of predictions. Finally, we discuss methodological issues in time prediction research and implications for research and application.