Recent years brought fast growth and fall of popularity of virtual worlds and virtual ventures. Many companies moved their activity to the virtual reality. Virtual worlds strongly increased their communities. Researches show that they influence on the real world activity. Selected problems...

In this study we analyze perception of authenticity by visitors of South Tyrol’s museum of archeology, best known as Ötzi museum, in the Autonomous Province of Bolzano (Italy). With the help of factor analysis we individuate two factors related to authenticity and study the determinants of...

The problem of multicollinearity in the assessments of coefficients is well established. However, it is rarely researched in the estimations of macroeconomic variables and economic performance of developing countries. Predicatively, it has impacts on the estimations of coefficients that should...

The present paper introduces results of an analysis conducted on data collected from Khartoum state for the year 2009. It aims to apply statistical models for the HIV/AIDS data in Khartoum state centers of testing blood and counseling. AIDS is recognized as an emerging disease only in the early...

Subgroup analysis is an integral part of comparative analysis where assessing the treatment effect on a response is of central interest. Its goal is to determine the heterogeneity of the treatment effect across subpopulations. In this paper, we adapt the idea of recursive partitioning and...

We study the United Nations Organization's Kyoto Protocol nations to address two questions. First of all, what are the environmental production efficiency rankings of these nations? Secondly, is there a relationship between a nation's ratification status and its environmental production...

This paper introduces the model confidence set (MCS) and applies it to the selection of models. An MCS is a set of models that is constructed so that it will contain the best model with a given level of confidence. The MCS is in this sense analogous to a confidence interval for a parameter. The...