Self-exciting threshold models for time series of counts with a finite range

In this article, an integer-valued self-exciting threshold model with a finite range based on the binomial INARCH(1) model is proposed. Important stochastic properties are derived, and approaches for parameter estimation are discussed. A real-data example about the regional spread of public drunkenness in Pittsburgh demonstrates the applicability of the new model in comparison to existing models. Feasible modifications of the model are presented, which are designed to handle special features such as zero-inflation.     

The Impact of Adolescents' Classroom and Neighborhood Ethnic Diversity on Same‐ and Cross‐Ethnic Friendships Within Classrooms

This study examines how classroom and neighborhood ethnic diversity affect adolescents' tendency to form same‐ versus cross‐ethnic friendships when they enter middle school. Hypotheses are derived from exposure, conflict, and constrict theory. Hypotheses are tested among 911 middle school students (43 classrooms, nine schools) in the Netherlands. Multilevel (p₂) social network analyses show that students were more likely to engage in same‐ethnic rather than cross‐ethnic friendships. In line with conflict theory, greater classroom and neighborhood diversity were related to stronger tendencies to choose same‐ethnic rather than cross‐ethnic friends, among both ethnic majority and minority students. Diversity did not hamper reciprocity, as students in more ethnically diverse classrooms were even more likely to reciprocate friendships.     

Determinants of in-group bias: Is group affiliation mediated by guilt-aversion?

In-group favoritism in social dilemma situations is one of Social Identity Theory’s main findings. We investigate what causes the in-group bias: is it merely due to group affiliation or, alternatively, is guilt-aversion moderating the strength of in-group favoring? We induce group membership in a minimal group setting, observe in-/out-group transfers and elicit corresponding beliefs. According to our experimental data group affiliation affects beliefs and explains a substantial part of the bias. Evidence for guilt-aversion is found only when beliefs are elicited before actions.     

Multiple tests for the performance of different investment strategies

In the context of modern portfolio theory, we compare the out-of-sample performance of eight investment strategies which are based on statistical methods with the out-of-sample performance of a family of trivial strategies. A?wide range of approaches is considered in this work, including the traditional sample-based approach, several minimum-variance techniques, a shrinkage, and a minimax approach. In contrast to similar studies in the literature, we also consider short-selling constraints and a risk-free asset. We provide a way to extend the concept of minimum-variance strategies in the context of short-selling constraints. A main drawback of most empirical studies on that topic is the use of simple testing procedures which do not account for the effects of multiple testing. For that reason we conduct several hypothesis tests which are proposed in the multiple-testing literature. We test whether it is possible to beat a trivial strategy by at least one of the non-trivial strategies, whether the trivial strategy is better than every non-trivial strategy, and which of the non-trivial strategies is significantly outperformed by naive diversification. The empirical part of our study is conducted using US stock returns from the last four decades, obtained via the CRSP database.     

‘Show me the money and the party!’ – variation in Facebook and Twitter adoption by politicians

Our study explores the adoption of Facebook and Twitter by candidates in the 2013 German Federal elections. Utilizing data from the German Longitudinal Election Study candidate survey fused with data gathered on the Twitter and Facebook use of candidates, we draw a clear distinction between Facebook and Twitter. We show that adoption of both channels is primarily driven by two factors: party and money. But the impact of each plays out differently for Facebook and Twitter. While the influence of money is homogenous for Facebook and Twitter with the more resources candidates have, the more likely they are to adopt, the effect is stronger for Facebook. Conversely, a party’s impact on adoption is heterogeneous across channels, a pattern we suggest is driven by the different audiences Facebook and Twitter attract. We also find candidates’ personality traits only correlate with Twitter adoption, but their impact is minimal. Our findings demonstrate that social media adoption by politicians is far from homogenous, and that there is a need to differentiate social media channels from one another when exploring motivations for their use.     

A semiparametric approach to hidden Markov models under longitudinal observations

We propose a hidden Markov model for longitudinal count data where sources of unobserved heterogeneity arise, making data overdispersed. The observed process, conditionally on the hidden states, is assumed to follow an inhomogeneous Poisson kernel, where the unobserved heterogeneity is modeled in a generalized linear model (GLM) framework by adding individual-specific random effects in the link function. Due to the complexity of the likelihood within the GLM framework, model parameters may be estimated by numerical maximization of the log-likelihood function or by simulation methods; we propose a more flexible approach based on the Expectation Maximization (EM) algorithm. Parameter estimation is carried out using a non-parametric maximum likelihood (NPML) approach in a finite mixture context. Simulation results and two empirical examples are provided.     

Qualitätsmanagement: Entwicklung,Problemfelder und ein integrativer Lösungsvorschlag

Quality Management: History, problems and an integrative modelStarting with a critical examination of the history and the commonly known concepts and systems of Quality Management, the paper discusses a broader understanding of quality in a genuinely managerial perspective. This is shown by generating and applying five basic dimensions of the quality concept. An integrative concept of Quality Management is presented.     

Robust, distribution-free inference for income share ratios under complex sampling

The quintile share ratio of disposable income is the primary inequality indicator of the European Union. As an inequality indicator, it must be sensitive to extreme large observations. Therefore, outliers have a strong impact on the bias and the variance of the classical quintile share ratio estimator. This may mislead the interpretation of income inequality. A class of estimators which are robust against outliers is introduced. They have a bounded influence function, they may reduce the bias incurred by the robustification and they reduce variability. Based on an asymptotic framework which respects the design-based, non-parametric approach, inference for these robust estimators is developed. A large simulation study with close to reality universes derived from the Statistics of Living Conditions Surveys of the EU allows to study the performance of the proposed estimators.     

Is Poker a Game of Skill or Chance? A Quasi-Experimental Study

Due to intensive marketing and the rapid growth of online gambling, poker currently enjoys great popularity among large sections of the population. Although poker is legally a game of chance in most countries, some (particularly operators of private poker web sites) argue that it should be regarded as a game of skill or sport because the outcome of the game primarily depends on individual aptitude and skill. The available findings indicate that skill plays a meaningful role; however, serious methodological weaknesses and the absence of reliable information regarding the relative importance of chance and skill considerably limit the validity of extant research. Adopting a quasi-experimental approach, the present study examined the extent to which the influence of poker playing skill was more important than card distribution. Three average players and three experts sat down at a six-player table and played 60 computer-based hands of the poker variant “Texas Hold’em” for money. In each hand, one of the average players and one expert received (a) better-than-average cards (winner’s box), (b) average cards (neutral box) and (c) worse-than-average cards (loser’s box). The standardized manipulation of the card distribution controlled the factor of chance to determine differences in performance between the average and expert groups. Overall, 150 individuals participated in a “fixed-limit” game variant, and 150 individuals participated in a “no-limit” game variant. ANOVA results showed that experts did not outperform average players in terms of final cash balance. Rather, card distribution was the decisive factor for successful poker playing. However, expert players were better able to minimize losses when confronted with disadvantageous conditions (i.e., worse-than-average cards). No significant differences were observed between the game variants. Furthermore, supplementary analyses confirm differential game-related actions dependent on the card distribution, player status, and game variant. In conclusion, the study findings indicate that poker should be regarded as a game of chance, at least under certain basic conditions, and suggest new directions for further research.