Analysis of Variance of Multiply Imputed Data

As a procedure for handling missing data, Multiple imputation consists of estimating the missing data multiple times to create several complete versions of an incomplete data set. All these data sets are analyzed by the same statistical procedure, and the results are pooled for interpretation. So far, no explicit rules for pooling F tests of (repeated-measures) analysis of variance have been defined. In this article we outline the appropriate procedure for the results of analysis of variance (ANOVA) for multiply imputed data sets. It involves both reformulation of the ANOVA model as a regression model using effect coding of the predictors and applying already existing combination rules for regression models. The proposed procedure is illustrated using 3 example data sets. The pooled results of these 3 examples provide plausible F and p values.     

Investigation of Multiple Imputation in Low-Quality Questionnaire Data

The performance of multiple imputation in questionnaire data has been studied in various simulation studies. However, in practice, questionnaire data are usually more complex than simulated data. For example, items may be counterindicative or may have unacceptably low factor loadings on every subscale, or completely missing subscales may complicate computations. In this article, it was studied how well multiple imputation recovered the results of several psychometrically important statistics in a data set with such properties. Analysis of this data set revealed that multiple imputation was able to recover the results of these analyses well. Also, a simulation study showed that multiple imputation produced small bias in these statistics for simulated data sets with the same properties.     

Influence of test anxiety on measurement of intelligence

In this study a measurement model for a test anxiety questionnaire was investigated in a sample of 207 Dutch students in the first grade of junior secondary vocational education. The results of a confirmatory factor analysis showed that a model for test anxiety with three factors for worry, emotionality, and lack of self-confidence is associated with a significantly better fit than a model comprised of only the first two factors. The relations of the three test anxiety factors to scores on intelligence tests for measuring verbal ability, reasoning, and spatial ability were examined. The results indicated that test anxiety appears to be transitory: the negative relation between test anxiety and test performance promptly fades away. Finally, we examined whether a distinction can be made between highly test anxious students with low performance due to worrisome thoughts (interference hypothesis) or low ability (deficit hypothesis). Results do not support the deficit hypothesis because the scores of all highly test anxious students increased in a less stressful situation.     

Therapist-controlled exposure in vivo versus self-controlled exposure in vivo: A comparison with obsessive-compulsive patients

Fourteen obsessive-compulsive clients were given treatment consisting of ten sessions of gradual exposure in vivo With half the clients, the exposure in vivo was therapist-controlled; with the other half, the exposure in vivo was self-controlled.

The results of the posttest showed that both versions of the treatment resulted in a significant improvement on the in vivo measurement, anxiety and avoidance scales, Leyton Obsessional Inventory, Self-Rating Depression Scale and anxious mood. Neither the posttest nor the follow-ups one month and 3.5 months later indicated a difference between the effects of the two conditions. Self-controlled exposure in vivo proved to be as effective as therapist-controlled exposure in vivo, in spite of the fact that in the latter condition each treatment session lasted twice as long as in the former condition.     

Proliferation of authors on research reports in medicine

Publication in the biomedical literature is important because it is the major pathway by which new concepts and discoveries are disseminated amongst scientists. In the last 30 years there has been a dramatic increase, not only in the volume of publications but in the number of authors per article as well. This paper summarizes the current literature on authorship and its proliferation in medicine. From the literature it becomes clear that for biomedical articles, the mean number of authors increased from 1.7 in 1960 to 3.1 in 1990, and there are indications that this trend is even greater in clinical medicine such that single authorship almost has disappeared. Formal guidelines of who should be considered an author have been set by the International Committee of Medical Journal Editors. There are studies suggesting that not all authors on multiauthor papers fulfill these criteria. Inappropriate multiple authorship leads to dilution of authorship responsibility and unjustified citation in curriculum vitae. Recommendations regarding the prevention of inappropriate authorship are given in this paper. This paper is adapted from a lecture presented to a Symposium on Scientific Integrity, Warsaw, Poland, 23 November 1995. Dr. Drenth is a clinical investigator and resident in internal medicine.     

The Interpretability Logic of all Reasonable Arithmetical Theories

This paper is a presentation of astatus quæstionis, to wit of the problemof the interpretability logic of all reasonablearithmetical theories.We present both the arithmetical side and themodal side of the question.Dedicated to Dick de Jongh on the occasion of his 60th birthday     

The empowering potential of intergroup leadership: How intergroup leadership predicts psychological empowerment through intergroup relational identification and resources

As work increasingly transcends organizational boundaries, employee psychological empowerment benefits from resources provided by others outside of the employee's own team, department, or organization. These intergroup collaborations, however, may be inhibited by social identity and social categorization processes, so that the empowerment potential of these relations remains largely untapped. In this study (N = 213), we demonstrate that intergroup leadership is linked to employee psychological empowerment via intergroup relational identification and access to resources. In this way, this study demonstrates the empowering potential of intergroup leadership and intergroup relational identification for employees who collaborate across group barriers. We finish this paper by discussing the main implications for both empowerment and intergroup leadership theory, suggesting fruitful avenues for future research and highlighting the practical value for those who are motivated to increase psychological empowerment among boundary-spanning employees.     

Pattern stability and error correction during in-phase and antiphase four-ball juggling

The authors studied pattern stability and error correction during in-phase and antiphase 4-ball fountain juggling. To obtain ball trajectories, they made and digitized high-speed film recordings of 4 highly skilled participants juggling at 3 different heights (and thus different frequencies). From those ball trajectories, the authors determined and analyzed critical events (i.e., toss, zenith, catch, and toss onset) in terms of variability of point estimates of relative phase and temporal correlations. Contrary to common findings on basic instances of rhythmic interlimb coordination, in-phase and antiphase patterns were equally variable (i.e., stable). Consistent with previous findings, however, pattern stability decreased with increasing frequency. In contrast to previous results for 3-ball cascade juggling, negative lag-one correlations for catch-catch intervals were absent, but the authors obtained evidence for error corrections between catches and toss onsets. That finding may have reflected participants' high skill level, which yielded smaller errors that allowed for corrections later in the hand cycle.     

Variation in reversal learning by three generalist mesocarnivores

Animal Cognition - Urbanization imposes novel challenges for wildlife, but also provides new opportunities for exploitation. Generalist species are commonly found in urban habitats, but the...