Testing for an excessive number of zeros in time series of bounded counts

For the modeling of bounded counts, the binomial distribution is a common choice. In applications, however, one often observes an excessive number of zeros and extra-binomial variation, which cannot be explained by a binomial distribution. We propose statistics to evaluate the number of zeros and the dispersion with respect to a binomial model, which is based on the sample binomial index of dispersion and the sample binomial zero index. We apply this index to autocorrelated counts generated by a binomial autoregressive process of order one, which also includes the special case of independent and identically (i. i. d.) bounded counts. The limiting null distributions of the proposed test statistics are derived. A Monte-Carlo study evaluates their size and power under various alternatives. Finally, we present two real-data applications as well as the derivation of effective sample sizes to illustrate the proposed methodology.     

Communication About Micropollutants in Drinking Water: Effects of the Presentation and Psychological Processes

This study investigates how people change their risk perception, trust, and behavior as a consequence of being informed about the occurrence of micropollutants in drinking water. Micropollutants are substances present in extremely low concentrations that might be dangerous in higher concentrations. Data were gathered in the city of Zurich, Switzerland in 2013 using a questionnaire in which the information on micropollutants was presented differently to 12 experimental groups. Data of the key constructs were gathered before and after this information, so that causal effects could be quantified by regression analyses. Affective reactions to the information turned out to be the critical mediator of changes in risk perception (operationalized as the perceived change of quality due to pollution), which is an important determinant of changes in behavior and trust. Also, direct effects of affective reactions on behavior and trust were observed. Trust before appraising risks reduces negative affective reactions; however, it also reduces perceived quality (i.e., increases risk perception) and trust after risks are appraised. The different forms of information mainly influenced the participants’ affective reactions, but they also influenced perceived quality. The presentation with the least negative effects was a comparison of the intake of the substance by water with intake by food. The experimental design with repeated measurement that considers trust as a determinant and consequence of risk perception uncovered positive and negative effects of trust before appraising risks on changes of risk perception and trust due to appraising risks.     

Plan Colombia: illegal drugs,economic development and counterinsurgency – a political economy analysis of Colombia's failed war

This article examines the socioeconomic effects of the illegal drug industry on economic and social development in Colombia. It shows that illegal drugs have fostered violence and have had a negative effect on economic development. This article also shows that the Plan Colombia anti‐drug policy has been an ineffective strategy in terms of decreasing drug production, generating economic development and reducing violence. Since this study includes both a statistical analysis of the effects that violence and illegal drugs have on the economic growth of Colombia, along with an evaluation of the Plan Colombia policy programme, it fills the gap between existing empirical studies of the Colombian illegal drug industry and specific analyses of Plan Colombia.     

Comparing Performance of Multiclass Classification Systems with ROC Manifolds: When Volume and Correct Classification Fails

Higher dimensional surfaces are used to examine the diagnostic performance of multiclass classification systems. These surfaces are extensions of the ROC curve and are known as ROC surfaces or manifolds. Manifolds may be constructed from either the correct classifications or from the misclassifications of the diagnostic system. Comparisons of the usefulness of each of these ROC manifolds with respect to the performance of the diagnostic system are made with emphasis on inferences from volume under the surface and optimal operating points (thresholds) of the system. Recommendations for when to use each type of ROC manifold and performance measure are discussed.     

Reliability and effects of muscular pretension on isometric strength of older adults

There were two objectives to this study: (a) to determine the reliability of measuring isometric maximum torque (MT) and maximum rate of torque development (MRTD) of the knee extensor and flexor muscles and (b) to assess the effects of different muscular pretensions on MT and MRTD of older adults. Maximum strength of 35 untrained healthy older adults (aged 66.9?±?6.6 years; height 1.72?±?0.07 m; weight 75.2?±?9.6 kg) was measured. Strength measurement was performed with the Dr. Wolff ISO Check using a piezo-electric force transducer. MT intra-day coefficient of variation (CV) was between 3.30 and 12.40 % for both measurement sessions. Intraclass correlation coefficients (ICC) ranging from 0.71 to 0.99 showed good relative reliability. MT test–retest reliability (between sessions 1 and 2) of knee extension reached a CV between 7.10 and 9.30 % and high ICC values. The measurement of the knee flexion achieved an acceptable CV (9.40 %) at 40 % muscular pretension. MRTD was negatively influenced by muscular pretension (p <0.05). In conclusion, MT could be measured reliably over different trials using isometric strength measurement. The test–retest reliability was acceptable at knee extension with 10 to 40 % muscular pretension and with 40 % muscular pretension at knee flexion. A higher muscular pretension has no impact on MT but decreases MRTD in older adults.     

Zur Messung von Forschungsqualit?t

This paper deals with the Forschungsrating (RWR) by the German Wissenschaftsrat (WR) in sociology. The WR??s objective in conducting this pilot study was to test a practice which allows a sophisticated assessment of the research facilities in Germany. Basically, two theses are exhibited towards the RWR in this paper: First, it seems possible that the published results are neither objective, nor reliable or valid because of implicit assessment procedures by the reviewers. Second we ask, whether a simple model of scientific quality, composed of a few quantitative indicators, yields similar results compared with the RWR. To empirically address these aspects, data of the RWR and our own standardized survey on the reputation of German research facilities is analyzed. Furthermore we conducted interviews with members of the group of reviewers. The results show that problems concerning the objectivity of analysis cannot be excluded. Our general conclusion about the reliability of the measurement, limited to the inner consistency of the quantitative indicators, is positive. A satisfactory reproduction of the RWR??s results solely based on quantitative data cannot be achieved. This is interpreted as a sign of minor validity. It is concluded that the amount and quality of data collected in the RWR, as well as the standardization of the rating process need to be improved.