Mixing patterns between age groups in social networks

We present a method for estimating transmission matrices that describe the mixing and the probability of infection between age groups. Transmission matrices can be used to estimate age-dependent forces of infection in age-structured, compartmental models for the study of infectious diseases. We analyze the social network generated by the synthetic population of Portland and extract mixing patterns. Our results show that the mixing within the population consists of two groups, children and adults. Children interact most frequently with other children close to their own age, while adults interact with a wider range of age groups and the durations of typical adult contacts are shorter than typical contacts between children. Furthermore, the transmission matrix shows that children are more likely to acquire infection than adults.     

Sicherheitsäquivalente zur risikoadjustierten Bewertung: Unternehmensexterne Bewertungssicht vs. unternehmensinterne Steuerungssicht Replik zu den Anmerkungen „Zum Verhältnis von Wertadditivität bei Sicherheitsäquivalenten und Risikoanalyse“ von <Emphasis Type="Italic">Reichling et al.</Emphasis> (2008)

Die Forderung nach schwacher Wertadditivit?t von Sicherheits?quivalenten ist in Abh?ngigkeit des jeweiligen Bewertungszwecks zu diskutieren. W?hrend in der unternehmensexternen Bewertungssicht, z.B. bei der Unternehmensbewertung, die Forderung nach schwacher Wertadditivit?t gut begründbar ist, stellt sie im Bereich der unternehmensinternen Steuerungssicht eine „Nice to have“-Anforderung dar. Darüber hinaus werden in der bisherigen Literatur zur Anwendbarkeit von Sicherheits?quivalenten die Kernherausforderungen der unternehmensinternen Steuerung vernachl?ssigt. Insbesondere die ad?quate Berücksichtigung stochastischer Abh?ngigkeiten im Portfolioverbund bei der Bewertung von Einzelgesch?ften mittels Sicherheits?quivalenten stellt eine Forschungslücke dar.     

Testing the Significance of Categorical Predictor Variables in Nonparametric Regression Models

In this paper we propose a test for the significance of categorical predictors in nonparametric regression models. The test is fully data-driven and employs cross-validated smoothing parameter selection while the null distribution of the test is obtained via bootstrapping. The proposed approach allows applied researchers to test hypotheses concerning categorical variables in a fully nonparametric and robust framework, thereby deflecting potential criticism that a particular finding is driven by an arbitrary parametric specification. Simulations reveal that the test performs well, having significantly better power than a conventional frequency-based nonparametric test. The test is applied to determine whether OECD and non-OECD countries follow the same growth rate model or not. Our test suggests that OECD and non-OECD countries follow different growth rate models, while the tests based on a popular parametric specification and the conventional frequency-based nonparametric estimation method fail to detect any significant difference.     

Discriminating characteristics of union members’ attitudes toward drug testing in the workplace

In this study of the acceptance by union members of drug testing in the workplace, 919 union members from 13 major unions were asked what drug-testing policy, if any, they preferred. Respondents evaluated particular aspects of a hypothetical drug-testing program. The results show that a large majority of union members agree with a limited drug-testing policy. Five theoretical models of union member attitudes were extrapolated to the drug-testing context and were examined by using discriminant function analysis. No support was found for the individual demographics theory, but empirical support was found for some elements of instrumental union, bargaining outcomes, general normative attitude, and workplace conditions theory. The discriminant function was 80.56 percent successful in classifying union members who accept drug testing.     

Facial expression in the presence of friends and strangers

This study investigated the effect of the physical presence of a friend or of a stranger on facial expressiveness. Pairs of friends and pairs of strangers (all women) were unobtrusively videotaped while they viewed together a number of emotional stimulus slides, and rated their individual emotional responses to them. Judges subsequently attempted to identify from the videotapes the emotions reported by each sender subject. Generally, expressions were more readily identified for women videotaped with friends than for those recorded with strangers. These results support the suggestion that the degree to which emotions are expressed depends on the role of an accompanying person. Altemative interpretations of this view are discussed.We thank Alan Fridlund and an anonymous reviewer for comments on a previous version of this paper.     

TEACHING TOOLS: COOPERATIVE LEARNING IN ECONOMICS

Cooperative learning is a structured, systematic instructional technique in which students work together in small groups toward a common goal. We demonstrate the effectiveness of cooperative learning with an illustrative example for teaching the labor supply curve. Recommendations for introducing the technique, forming groups, the instructor's role during group work, grading and extensions of cooperative learning to other topics are discussed.     

A simple recursive estimation method for linear regression models with AR(p) disturbances

An exact transformation that reduces the AR(p) process into white noise is well known in statistics, see Fuller (1976). However, practitioners still use and econometric textbooks still recommend the Cochrane-Orcutt procedure for p>2, see Greene (1990). This paper derives an alternative exact transformation for the AR(p) process which is computationally simple. Based on this transformation, a GLS estimator is proposed, requiring only least squares regressions and recursive computations. This is illustrated for the AR(3) case.