Collinearity diagnostic applied in ridge estimation through the variance inflation factor

The variance inflation factor (VIF) is used to detect the presence of linear relationships between two or more independent variables (i.e. collinearity) in the multiple linear regression model. However, the traditionally used VIF definitions encounter some problems when extended to the case of the ridge estimation (RE). This paper presents an extension of the VIF in RE by providing two alternative VIF expressions that overcome these problems in the general case. Some characteristics of these expressions are also presented and compared with the traditional expression. The results are illustrated with an economic example in the case of three independent variables and with a Monte Carlo simulation for the general case.     

Optimal sequential Bayesian analysis for degradation tests

Degradation tests are especially difficult to conduct for items with high reliability. Test costs, caused mainly by prolonged item duration and item destruction costs, establish the necessity of sequential degradation test designs. We propose a methodology that sequentially selects the optimal observation times to measure the degradation, using a convenient rule that maximizes the inference precision and minimizes test costs. In particular our objective is to estimate a quantile of the time to failure distribution, where the degradation process is modelled as a linear model using Bayesian inference. The proposed sequential analysis is based on an index that measures the expected discrepancy between the estimated quantile and its corresponding prediction, using Monte Carlo methods. The procedure was successfully implemented for simulated and real data.     

Max–min optimal discriminating designs for several statistical models

In the literature, different optimality criteria have been considered for model identification. Most of the proposals assume the normal distribution for the response variable and thus they provide optimality criteria for discriminating between regression models. In this paper, a max–min approach is followed to discriminate among competing statistical models (i.e., probability distribution families). More specifically, k different statistical models (plausible for the data) are embedded in a more general model, which includes them as particular cases. The proposed optimal design maximizes the minimum KL-efficiency to discriminate between each rival model and the extended one. An equivalence theorem is proved and an algorithm is derived from it, which is useful to compute max–min KL-efficiency designs. Finally, the algorithm is run on two illustrative examples.     

Influence diagnostic analysis in the possibly heteroskedastic linear model with exact restrictions

The local influence method has proven to be a useful and powerful tool for detecting influential observations on the estimation of model parameters. This method has been widely applied in different studies related to econometric and statistical modelling. We propose a methodology based on the Lagrange multiplier method with a linear penalty function to assess local influence in the possibly heteroskedastic linear regression model with exact restrictions. The restricted maximum likelihood estimators and information matrices are presented for the postulated model. Several perturbation schemes for the local influence method are investigated to identify potentially influential observations. Three real-world examples are included to illustrate and validate our methodology.     

Spatial–temporal modellization of the $$\hbox {NO}_{2}$$ concentration data through geostatistical tools

The nitrogen dioxide is a primary pollutant, regarded for the estimation of the air quality index, whose excessive presence may cause significant environmental and health problems. In the current work, we suggest characterizing the evolution of \(\hbox {NO}_{2}\) levels, by using geostatistical approaches that deal with both the space and time coordinates. To develop our proposal, a first exploratory analysis was carried out on daily values of the target variable, daily measured in Portugal from 2004 to 2012, which led to identify three influential covariates (type of site, environment and month of measurement). In a second step, appropriate geostatistical tools were applied to model the trend and the space–time variability, thus enabling us to use the kriging techniques for prediction, without requiring data from a dense monitoring network. This methodology has valuable applications, as it can provide accurate assessment of the nitrogen dioxide concentrations at sites where either data have been lost or there is no monitoring station nearby.     

Political practice and the rise of an ethnic enclave

Summary The Cuban American community shares many of the structural features commonly associated with other types of immigrant enclaves. But its specific mode of political incorporation into the United States distinguishes it from other enclaves, making it a unique sociopolitical formation: authoritarian enclave. The Cuban American enclave arose out of Caribbean geopolitics as an unintentional byproduct of four state-sponsored movements. These movements interlocked in an uneven manner, sometime via the civil, other times via the military, and still other times based on a combination of both. The internally divided Batistianist movement interlocked via its military wing with Trujillo's relatively unified Dominican state. In contrast, the highly unified Conservative movement interlocked with the military wing of the internally divided U.S. state. The Liberal movement, like the previous movement, was internally unified but, unlike them, its contacts were with the civil, not military, wing of the U.S. state. Preliminary research on the Terrorist movement, a community-generated movement that responds to changing geopolitical situations, suggests that its civil and military wing are discreetly and flexibly linked to each other. These movements had the cumulative and unintentional effect of creating a new organizational space within the Caribbean geopolitical system from which the Cuban American community was later to emerge. The Cuban American enclave rooted in Miami is today an important actor in the Caribbean Basin.The four movements under review left an indelible imprint on the material and ideational contours of the enclave. The Batistianists, Conservatives, and Terrorists contributed to the formation of an emigre moral economy where politics and profit were fused. The Batistianists, by investing their smuggled capital in the Miami area, by relying on the civil wing of their movement to rejuvenate old allegiances and networks, and by boycotting and harassing politically heterodox merchants, established a type of political monopoly over the local economy. The Conservatives, by misappropriating C.I.A. funds and reselling weapons, learned the art of buying and selling, developed sympathetic sources of credit from politically like-minded militants, and gathered enough investment capital to establish small enterprises in the Miami area. The Terrorists, by bombing Liberal merchants, prevented their discourse from gaining a local material base of power. The militant Liberals, through their inactivity in the community, facilitated, unintentionally, the rise of the enclave.The community's collective identity and sources of normative integration remain partly rooted in its militant past. Batistianism, Conservatism, and Terrorism, with its characteristic concerns for custom, patriotism, anti-communism, order, and community, concerns which have always been lacking in Liberal thought, a current of thought that in any case never circulated widely in the community, contributed, ironically enough, to the enclave's subsequent success. If the enclave entrepreneur can today invoke collective claims in order to legitimize his patriarchal system of capital-labor relations and contribute to group cohesion, it is because the militants and terrorists had earlier inculcated the community with these very same notions. In the next few years the Cuban American entrepreneurs, the community's leading strata, will need to generate a new set of ideal interests similar to the ones they inherited from their predecessors.The extreme conservatism of the Cuban Americans is in direct opposition to the political practices of all other immigrant groups, enclave or otherwise. Immigrant groups tend to support politically liberal causes and, among recent arrivees, this tendency is even more pronounced. But the Cuban American enclave, itself a relatively recent group, defies this pattern. But the mid-1970s the Cuban Americans had established themselves as the single most conservative minority group in the United States. Cuban American exceptionalism is not, as some neo-Marxists scholars have claimed, the product of their privileged background in Cuba nor their relative economic success in the United States. Political practices, after all, cannot be deduced from simple market locations. Cuban American conservatism was constructed during the early years of community formation as the result of the interaction of discourse and power.The community's shift toward extreme conservatism runs counter to the early composition of the exiles. Recall that in demographic-political terms the base of the community shifted in 1962 from the Batistianists and Conservatives, to the Liberals. The political practices of the community, however, travelled a reverse path: from Liberal, to Conservative and Batistianist. Political practice, in other words, had defied the very same organizational and demographic determinants that until now had served to structure its existence. Emigre politics had become unhinged from its base and was flowing downwards and shaping the material and ideal interests of the community at a time when it was undergoing a transition from exile to ethnic minority. The discursive practices and power maneuvers of the Batistianists and Conservatives infused the community's collective identity, economic life, and group cohesiveness with their own moral-political preferences. The Liberals, due to their insurrectionary strategy, failed to do so. During deactivation, the Liberals who advocated normalizing relations with Cuba successfully disorganized Conservative thought, but the Terrorists prevented them from circulating their views or gaining local power. Thus, emigre politics preceded the rise of ethnic markets and the availability of federal aid, and influenced Cuban American group and identity formation.The Cuban American community, to summarize my argument, is an expression of exploitation and domination along with representation. In typological terms, the community ought to be characterized as an authoritarian enclave, a type of formation that fuses economic entrepreneurship, social communalism, and authoritarian politics. Those unacquainted with the Cuban American community sometimes view it as a sociological aberration, an idiosyncratic enclave when compared to other ones in the United States, yet its trajectory reconfirms two of history's oldest lessons: the boundaries of nations and states rarely coincide; and, words and silences matter... as does power.

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A Methodology for Risk Analysis Based on Hybrid Bayesian Networks: Application to the Regasification System of Liquefied Natural Gas Onboard a Floating Storage and Regasification Unit

This article presents an iterative six‐step risk analysis methodology based on hybrid Bayesian networks (BNs). In typical risk analysis, systems are usually modeled as discrete and Boolean variables with constant failure rates via fault trees. Nevertheless, in many cases, it is not possible to perform an efficient analysis using only discrete and Boolean variables. The approach put forward by the proposed methodology makes use of BNs and incorporates recent developments that facilitate the use of continuous variables whose values may have any probability distributions. Thus, this approach makes the methodology particularly useful in cases where the available data for quantification of hazardous events probabilities are scarce or nonexistent, there is dependence among events, or when nonbinary events are involved. The methodology is applied to the risk analysis of a regasification system of liquefied natural gas (LNG) on board an FSRU (floating, storage, and regasification unit). LNG is becoming an important energy source option and the world's capacity to produce LNG is surging. Large reserves of natural gas exist worldwide, particularly in areas where the resources exceed the demand. Thus, this natural gas is liquefied for shipping and the storage and regasification process usually occurs at onshore plants. However, a new option for LNG storage and regasification has been proposed: the FSRU. As very few FSRUs have been put into operation, relevant failure data on FSRU systems are scarce. The results show the usefulness of the proposed methodology for cases where the risk analysis must be performed under considerable uncertainty.     

Bayesian estimation of incomplete data using conditionally specified priors

In this article, a class of conjugate prior for estimating incomplete count data based on a broad class of conjugate prior distributions is presented. The new class of prior distributions arises from a conditional perspective, making use of the conditional specification methodology and can be considered as the generalization of the form of prior distributions that have been used previously in the estimation of incomplete count data well. Finally, some examples of simulated and real data are given.     

Preference reversals: Time and again

This paper sheds new light on the preference reversal phenomenon by analyzing decision times in the choice task. In a first experiment, we replicated the standard reversal pattern and found that choices associated with reversals take significantly longer than non-reversals, and non-reversal choices take longer whenever long-shot lotteries are selected. These results can be explained by a combination of noisy lottery evaluations (imprecise preferences) and an overpricing phenomenon associated with the compatibility hypothesis. The first cause explains the existence of reversals, while the second explains the predominance of a particular type thereof. A second experiment showed that the overpricing phenomenon can be shut down, greatly reducing reversals, by using ranking-based, ordinally-framed evaluation tasks. This experiment also disentangled the two determinants of reversals, because imprecise evaluations still deliver testable predictions on decision times even in the absence of the overpricing phenomenon. Strikingly, when unframed ranking tasks were used, decision times in the choice phase were greatly reduced, even though this phase was identical across treatments. This observation is consistent with psychological insights on conflicting decision processes.