Some applications of nonlinear and non-Gaussian state–space modelling by means of hidden Markov models

Nonlinear and non-Gaussian state–space models (SSMs) are fitted to different types of time series. The applications include homogeneous and seasonal time series, in particular earthquake counts, polio counts, rainfall occurrence data, glacial varve data and daily returns on a share. The considered SSMs comprise Poisson, Bernoulli, gamma and Student-t distributions at the observation level. Parameter estimations for the SSMs are carried out using a likelihood approximation that is obtained after discretization of the state space. The approximation can be made arbitrarily accurate, and the approximated likelihood is precisely that of a finite-state hidden Markov model (HMM). The proposed method enables us to apply standard HMM techniques. It is easy to implement and can be extended to all kinds of SSMs in a straightforward manner.     

Robust variable selection with application to quality of life research

A large database containing socioeconomic data from 60 communities in Austria and Germany has been built, stemming from 18,000 citizens’ responses to a survey, together with data from official statistical institutes about these communities. This paper describes a procedure for extracting a small set of explanatory variables to explain response variables such as the cognition of quality of life. For better interpretability, the set of explanatory variables needs to be very small and the dependencies among the selected variables need to be low. Due to possible inhomogeneities within the data set, it is further required that the solution is robust to outliers and deviating points. In order to achieve these goals, a robust model selection method, combined with a strategy to reduce the number of selected predictor variables to a necessary minimum, is developed. In addition, this context-sensitive method is applied to obtain responsible factors describing quality of life in communities.     

Robust nonparametric tests for the two-sample location problem

We construct and investigate robust nonparametric tests for the two-sample location problem. A test based on a suitable scaling of the median of the set of differences between the two samples, which is the Hodges-Lehmann shift estimator corresponding to the Wilcoxon two-sample rank test, leads to higher robustness against outliers than the Wilcoxon test itself, while preserving its efficiency under a broad range of distributions. The good performance of the constructed test is investigated under different distributions and outlier configurations and compared to alternatives like the two-sample t-, the Wilcoxon and the median test, as well as to tests based on the difference of the sample medians or the one-sample Hodges-Lehmann estimators.     

Bilanzmanipulation und Managementpräferenzen bezüglich der Strenge des Systems der Rechnungslegungsregulierung

The present paper analyses the political economy of accounting regulation. It develops a game theoretic model of earnings management in a capital market context. Various forms of information asymmetry are examined. The analysis shows that the preferences of managers over the strictness of accounting regulation depend on the nature of the information asymmetry. In a number of instances, managers prefer to be subject to strict regulation. This result contradicts the often heard assertion that managers prefer lax regulation and has implications for regulatory competition.     

Comparison of multiple imputation and two-phase logistic regression to analyse two-phase case–control studies with rich phase 1: a simulation study

Two-phase case–control studies cope with the problem of confounding by obtaining required additional information for a subset (phase 2) of all individuals (phase 1). Nowadays, studies with rich phase 1 data are available where only few unmeasured confounders need to be obtained in phase 2. The extended conditional maximum likelihood (ECML) approach in two-phase logistic regression is a novel method to analyse such data. Alternatively, two-phase case–control studies can be analysed by multiple imputation (MI), where phase 2 information for individuals included in phase 1 is treated as missing. We conducted a simulation of two-phase studies, where we compared the performance of ECML and MI in typical scenarios with rich phase 1. Regarding exposure effect, MI was less biased and more precise than ECML. Furthermore, ECML was sensitive against misspecification of the participation model. We therefore recommend MI to analyse two-phase case–control studies in situations with rich phase 1 data.     

Application of Social Science Knowledge to the Community Organization Field

Community organization graduates of the School of Social Work, University of Washington, from 1966 to 1971, found a ready market for their skills although there was evidence of some slackening of demand and broader diversification of initial employment settings in the last two years. Graduates moved rapidly into administrative and management levels and appeared relatively stable in terms of interagency and geographical mobility. The small number of ethnically identified graduates made meaningful comparisons difficult. Sex, however, was a disadvantaging factor in employability and subsequent status. Of the ninety-one graduates surveyed, 94.5 percent responded Similar follow-up study of graduates in other geographic regions was recommended     

State standards for domestic violence perpetrator treatment: current status, trends, and recommendations

We empirically surveyed and analyzed existing standards for the treatment of perpetrators of domestic violence across the United States. Specific areas examined included: presence and scope; administrative entity for certifying; screening and risk assessment protocols; minimum length of treatment; theoretical or conceptual orientation; treatment content; preferred or allowable modalities of treatment; whether research findings are mentioned; methods for revising standards; and minimum education and training required for providers. We examined trends using several methods including comparisons between present and previous survey data (Maiuro et al., 2001). Positive trends were evident including increased use of multivariate models of treatment content, use of an intake assessment prior to treatment, use of a danger/lethality assessment to manage risk, recognition of the need for program evaluation and supportive research, and the requirement of a minimum level of formal education as a prerequisite for providers. We identify specific areas for further research and development and make recommendations for improving existing practice and standards of care.     

Demokratie für den Irak?

The situation in Iraq remains unstable. This is, among other factors, due to the lack of a realistic, long-term and integrative model for democratization. The current occupying powers neither dispose of a long-term plan, appropriate to the local circumstances, which could be able to include systematically local culture and social forms. Nor do they obviously have a clear step-by-step plan within the framework of an integral model which could take into account the experience of the past decades regarding sustainable democratization of Islamic core areas. This essay presents the three currently most promising and most realistic models of how Iraq can be democratized by means of a long-term, comprehensive, holistic and systematically differentiated strategy. The focus of attention is on the methodical inclusion of cultural, socio-psychological and sociological aspects. The three democratization models for Iraq are: 1) the Tatarstan model, 2) the Turkey model, 3) the model of stratified democracy. These three models are critically discussed and evaluated; in conclusion a short outlook will be drafted.     

Risk Management in a Polio-Free World

Inherent in the decision to launch the Global Polio Eradication Initiative in 1988 was the expectation for many people that immunization against poliomyelitis would eventually simply stop, as had been the case with smallpox following its eradication in 1977. However, the strategies for managing the risks associated with a "polio-free" world must be continuously refined to reflect new developments, particularly in our understanding of the live polioviruses in the oral poliovirus vaccine (OPV) and in the international approach to managing potential biohazards. The most important of these developments has been the confirmation in 2000 that vaccine-derived polioviruses (VDPVs) can circulate and cause polio outbreaks, making the use of OPV after interruption of wild poliovirus transmission incompatible with a polio-free world. A comprehensive strategy has been developed to minimize the risks associated with eventual OPV cessation, centered on appropriate long-term biocontainment of poliovirus stocks (whether for vaccine production, diagnosis, or research), the controlled reintroduction of any live poliovirus vaccine (i.e., from an OPV stockpile), and appropriate use of the inactivated poliovirus vaccine (IPV). Although some aspects of this risk management strategy are still debated, there is wide agreement that no strategy would entirely eliminate the potential risks to a polio-free world. The current strategy for risk management in a polio-free world will continue to evolve with better characterization of these risks and the development of more effective approaches both to reduce those risks and to limit their consequences should they occur.