Some remarks on the physical models concerning two different approaches to inference in statistical process control

Summary For technological applications it can be useful to identify some simple physical mechanisms, which, on the basis of the available knowledge of the production process, may suggest the most appropriate approach to statistical control of the random quantities of interest. For this purpose the notion of rupture point is introduced firstly. A rupture point is characterized bym randomly arising out of control states, assumed to be mutually exclusive and stochastically independent. Shewhart's control charts seem to represent the natural statistical tool for controlling a rupture point; however it is shown that they are fully justified only when the hazard rates attached to the causes of failure are constant. Otherwise, typically in the presence of time increasing hazard rates, Shewhart's control charts should be completed by a preventive intervention rule (preventive maintenance). In the second place, the notion of dynamic instability point is introduced, which is specifically characterized by assuming that the random quantity of interest is ruled by a stochastic differential equation with constant coefficients. By discretization, developed according to a possibly new approach, it is shown that the former model reduces to an equation error model, which is among the simplest used in adaptive control, and thus particularly easy to deal with in regard to parameter estimation and the definition of the optimum control rule.     

Analysing the information embedded in the optimal mean–variance weights: CAPM versus Bamberg and Dorfleitner model

This paper is centred on the analysis of the information embedded in the optimal weights of the assets in the CAPM and the Bamberg–Dorfleitner model. On this basis, first we find a functional relationship between the optimal weights of both models. Next, we find a set of performance indicators that express the contribution of each asset to the reward/volatility ratio measured as the Sharpe ratio or through a utility function. For the Bamberg–Dorfleitner model these indicators also lead to identify the contribution of each independent variable to the reward/volatility ratio. Technically, these connections are obtained through the covariance-normalized portfolio that consists of a transformation of the inverted covariance matrix. The additive property of covariances is transmitted to the indicators. These results enable investors and portfolio managers to obtain a precise knowledge of the causes of the value of the reward/volatility ratio. From the corporate point of view, this approach contributes to a better identification of the features of the different types of investors to whom to focus the corporate financial policy.     

Marital Quality Assessment: Reviewing the Concept,Instruments, and Methods

Abstract

This study aimed to investigate which instruments have been used in marital quality research since 2005, and the concepts underlying each measure. We conducted a literature review in the following databases: PsycINFO, PubMed, Web of Science, and BVS. The review included 91 studies investigating 21 instruments. Half of the scales were multidimensional, but the most used instruments were unidimensional, except for the DAS. Most measures had exploratory evidence of construct validity and did not provide a definition of the construct under evaluation. Theoretical development is needed to address the problem of largely subjective, empirically based measures. We suggest network models can help to develop new measures and to provide a fresh understanding of the construct and the dynamics of marital relations.     

DISCRETE CHOICE WITH SOCIAL INTERACTIONS AND ENDOGENOUS MEMBERSHIPS

This paper is about selection of neighbors in models of social interactions. I study a general equilibrium model of behavior subject to endogenous social influences when heterogeneous individuals can choose whom to associate with, buying associations on a “memberships market”. Social effects in behavior turn out to be a stratifying force: The desire for valuable interactions induces inefficient sorting and may lead to the endogenous emergence of “social traps”. The theory is then used to suggest identification strategies that may solve, in a micro‐founded way, identification and selection problems that typically affect empirical work on social interactions. Such strategies offer a viable alternative when valid instrumental variables or randomized experiments are not available. (JEL: C26, D85, Z13, Z19)     

The imbalance of sex-hormones related to depressive symptoms in obese men

Obese men may present hypogonadothrofic hypogonadism, mainly related to higher insulinemia and aromatase activity. Our objectives were to evaluate the relationship of sex-hormones profiles and frequency of depressive symptoms in 43 obese men, in a cross-sectional study. They had 19–60 years, and body mass index 30–50?kg/m². LH, total and free testosterone (TT and FT), estradiol (E₂), sex hormone binding globulin, estradiol/total testosterone ratio (E₂/T) were analyzed. Depressive symptoms were evaluated by “beck depression inventory” (BDI), and significant depression was considered if BDI?≥?16.Thirty-four (80%) presented low TT levels, but only 4 (14%) had low free testosterone and hypogonadism symptoms; 12 of 43 (28%) presented increased E₂. Forty five (56%) presented depressive symptoms, but 16 (28% of the 45) had significant depression. BDI correlated positively with E₂ (r?=?0.407; p?=?0.001) and E₂/T (r?=?0.473; p?=?0.001), but not TT or FT. Patients with significant depressive showed higher levels of estradiol (136?±?48 versus 103?±?48?pg/ml, p?=?0.02) and E₂/T (16.0?±?9.9 versus 9.8?±?4.6; p?=?0.002) (mean?±?SD).In conclusion, obese men may present relatively excess of estradiol and deficiency in testosterone, leading to an imbalance between these two hormones. The greater this imbalance, the more depressive symptoms had our patients.