Social and Educational Impact from the Introduction of National Exams in Greek High Schools: First Findings

In 1997 the Greek Government introduced a law by which the assessment of the students in Greek Lyceums (High Schools) changed. According to the new law the assessment of the 10th and the 11th grade students is based, for the first time, not only on their in school performance as assessed by their teachers but also on national written exams taken by all students in all subjects taught in school. The overall assessment will then be used as the only factor taken into account for entrance to higher education institutions. The new system was used for the first time in the year 1998-1999 and the first national exams for the 11th grade of all Greek High Schools took place in June 1999. In this paper we present the results of a survey that was conducted in September 1999 to assess the performance of students of the 11th grade as well as of students of the 10th grade in order to ascertain the first educational and social implications of the new system. This study is the first attempt in this direction. A comparison is also presented of the performance of students in the school year 1998-1999 to the results of the previous year 1997-1998, when no national exams were used.Educational systems, Mean grade in exams, Percentage of failure in exams, Region of schools, Size of schools, Type of schools

Influential Mathematicians: Birth, Education and Affiliation

Research output and impact is currently the focus of serious debate worldwide. Quantitative analyses based on a wide spectrum of indices indicate a clear advantage of US institutions as compared to institutions in Europe and the rest of the world. However the measures used to quantify research performance are mostly static: Even though research output is the result of a process that extends in time as well as in space, indices often only take into account the current affiliation when assigning influential research to institutions. In this paper, we focus on the field of mathematics and investigate whether the image that emerges from static indices persists when bringing in more dynamic information, through the study of the "trajectories" of highly cited mathematicians: birthplace, country of first degree, country of PhD and current affiliation. While the dominance of the US remains apparent, some interesting patterns -that perhaps explain this dominance- emerge

A Simulation Study on the Performance of Extreme-Value Index Estimators and Proposed Robustifying Modifications

The key issue of extreme-value theory is the estimation of a parameter γ, known as extreme value index. In this paper we review several extreme-value index estimators, ranging from the oldest ones to the most recent developments. Moreover, a smoothing procedure of these estimators are presented. A simulation study is conducted in order to compare the behaviour of the estimators and their smoothed alternatives. Maybe the most prominent results of this study is that no uniformly best estimator exists and that the behaviour of estimators depends on the value of the parameter γ itself.Extreme value index, Semi-parametric estimation, Smoothing modification

A Binomial Distribution With Dependent Trials And Its Use in Stochastic Model Evaluation

A model of Markov dependent trials is considered that leads to a generalization of the binomial distribution in the context of evaluating models of a time series by exploiting the sequential nature of model-based predictions. Adopting an evaluation method similar in nature to that suggested by Xekalaki & Katti (1984), the behaviour of the model is assigned a score that reflects the concordance or discordance of predicted and observed values for each of a sequence of points in time. The resulting series of scores leads to a final rating which is considered as a measure of the predictive ability of the model. The Markov dependent distribution is used to develop exact theory for the construction of confidence intervals and for testing hypotheses pertaining to the forecasting protential of a model. Some asymptotic theory is also developed.Model evaluation, Model validation, Dependent Bernouli trials, Forecasting models

Analysis and Comparison of Greek Parliamentary Electoral Systems of the Period 1974-1999

An important topic, in electoral studies, is the choice of the electoral system, which will be applied in parliamentary elections, because parliamentary seats distributed to political parties differ when a different system is applied. In this paper we focus on the five latest electoral systems applied in Greek Parliamentary Elections. Each one of them is described and analysed, in detail. Different measures of disproportionality are used in order to evaluate and compare these systems. We provide implementation details and illustrations using the data set of the latest parliamentary elections of 1996 and various data sets generated by introducing noise to the initial data setElectoral system, Measures of disproportionality, Sensitivity analysis

Assessing scientific research performance and impact with single indices

We provide a comprehensive and critical review of the h-index and its most important modifications proposed in the literature, as well as of other similar indicators measuring research output and impact. Extensions of some of these indices are presented and illustrated.Citation metrics, Research output, h-index, Hirsch index, h-type indices

Autoregressive Conditional Heteroskedasticity Models and the Dynamic Structure of the Athens Stock Exchange

Autoregressive Conditional Heteroskedasticity (ARCH) models have been applied in modeling the relation between conditional variance and asset risk premium. The most important theoretical regularities that govern the dynamic structure of financial time series are presented. A model named Exponential E-GARCH in Mean tests their validity in Athens Stock Exchange. The model fits well in Greek Stock Market, from 31 July 1987 to 30 July 1999, and provides empirical evidence on theoretical regularities. We find evidence for the existence of a positive trade-off (possible non-linear) between stock returns and volatility, the absence of “leverage effects”, the thick tailed stock returns distribution, the slower rate information accumulation when the market is closed than when it is open, the existence of positive non-synchronous trading effects and the existence of a long-term memory pattern in stock returns.

Extreme Value Analysis of Teletraffic Data

An empirically verified characteristic of the expanding area of Internet is the longtailness of phenomena such as cpu time to complete a job, call holding times, files lengths requested, inter-arrival times and so on. Extreme values of the above quantities are liable to cause problems to the efficient operation of the network and call for effective design and management. Extreme-value analysis is an area of statistical analysis particularly concerned with the systematic study of extremes, providing useful insight to fields where extreme values are probable to occur and have detrimental effects, as is the case of teletraffics. In this paper we illustrate the main elements of this analysis and proceed to a detailed application of extreme-value analysis concepts to a specific teletraffic data set. This analysis verifies, too, the existence of long tails in the data.Teletraffic engineering, Long tails, Extreme-value index, Smoothing procedures

Assessment of School Effectiveness in Greece using Multilevel Models

In recent years, a lot of attention has been given to the so-called “performance indicators”, which are primarily used for institutional comparisons. Education and health are the area in which these indicators are widely applied, serving the needs of modern societies for highly qualified rendering of servicesMultilevel modeling, Hierarchical data, Performance indicators, School effectiveness

Aspects of Estimation Procedures at Eurostat with Some Emphasis on Over-Space Harmonisation

It is of high interest for Eurostat, the investigation of the different estimation procedures that are applied, or discussed, internally. We focus our interest on three estimation domains i.e. the micro-aggregation techniques for producing confidential data, the backward calculation methods for obtaining homogeneous time series and some aspects of the sampling procedures that are discussed by Eurostat and are applied in the Member State level. With regard to each domain of estimation, we describe the different estimation procedures that are applied and the criteria for assessing the quality of the results obtained, and we make some proposals for the adoption of better practices. Due to the multinational character of the third estimation domain and in order to achieve the targets of our description, we used as exploratory tools three sample surveys that are conducted in all Member State i.e. the Labour Force survey, the European Household Panel survey and the Household Budget survey. Especially for those estimation domains that are applied at National level, we examined attempts that aim at the over space harmonization of the estimation procedures or of the measured concepts, and the role that Eurostat adopts in relation to those harmonization attempts