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Volume 7, Issue 2 - June 30, 2012
JAQM Volume 7, Issue 2 - June 30, 2012
Estimation Methods for the Structural Equation Models: Maximum Likelihood, Partial Least Squares and Generalized Maximum Entropy (p )
The concept of Latent Variables (LVs or latent constructs) is, probably, one of the most charming and discussed of the last fifty years, although, even today, it is only possible to give a negative definition of it: what is not observable, lacking both of origin and of measurement unit. One of the difficulties for a researcher in the economic-social sciences in the specification of a statistical model describing the casual-effect relationships between the variables derives from the fact that the variables which are object of the analysis are not directly observable (i.e. latent), for example, the performance, the customer satisfaction, the social status etc. Although such latent variables cannot be directly observable, the use of proper indicators (i.e. manifest variables, MVs) can make the measurement of such constructs easy. Thanks to the SEM, it is possible to analyze simultaneously, both the relations of dependence between the LVs (i.e, Structural Model), and the links between the LVs and their indicators, that is, between the corresponding observed variables (i.e, Measurement Model). The different and proper methodologies of estimate of the dependence are topics of this work. In particular, the aim of this work is to analyze Structural Equation Models (SEM) and, in particular, some of the different estimation methods mostly adopted: the Maximum Likelihood-ML, the Partial Least Squares- PLS and the Generalized Maximum Entropy - GME, by illustrating their main differences and similarities.
Evaluating Security Threats in Distributed Applications Lifestages (p )
Catalin Alexandru TANASIE,
Eduard Emanuel HERTELIU
The article starts with the classification of security threats as related to the context of operating distributed IT&C applications – DIAs, as concerning users, processes and the information exchanged. Security risks induced as part of the analysis, design and development phases of distributed application building are detailed alongside proposed countermeasures. A model addressing security element interaction is presented and details on its implementation as part of the authentication module of the model testing and refining application, MERICS, is shown.
Book Review on PIATA MUNCII INTRE FORMAL SI INFORMAL (LABOUR MARKET BETWEEN FORMAL AND INFORMAL) by Silvia PISICA, Valentina VASILE and Vergil VOINEAGU (p )
National economy is functioning and generates results both in formal (“official”) area and in the informal (“unregulated”, “unofficial”, “unstructured”) area of the economy. The informal sector exists, to a higher or lower extent, in all modern economies. It generates results, creates jobs, entails population income and is conditioning a significant part of consumption expenditure, while its presence contradicts the experts’ predictions, formulated few decades ago, on its predictable reduction and extinction as national economies develop themselves. The study on the informal sector of the economy presents both a theoretical interest for economics, and a practical one as well.