Accurate computation of single and product moments of order statistics under progressive censoring

An accurate procedure is proposed to calculate approximate moments of progressive order statistics in the context of statistical inference for lifetime models. The study analyses the performance of power series expansion to approximate the moments for location and scale distributions with high precision and smaller deviations with respect to the exact values. A comparative analysis between exact and approximate methods is shown using some tables and figures. The different approximations are applied in two situations. First, we consider the problem of computing the large sample variance–covariance matrix of maximum likelihood estimators. We also use the approximations to obtain progressively censored sampling plans for log-normal distributed data. These problems illustrate that the presented procedure is highly useful to compute the moments with precision for numerous censoring patterns and, in many cases, is the only valid method because the exact calculation may not be applicable.     

Computing maximum likelihood estimates from type II doubly censored exponential data

It is well-known that, under Type II double censoring, the maximum likelihood (ML) estimators of the location and scale parameters, θ and δ, of a twoparameter exponential distribution are linear functions of the order statistics. In contrast, when θ is known, theML estimator of δ does not admit a closed form expression. It is shown, however, that theML estimator of the scale parameter exists and is unique. Moreover, it has good large-sample properties. In addition, sharp lower and upper bounds for this estimator are provided, which can serve as starting points for iterative interpolation methods such as regula falsi. Explicit expressions for the expected Fisher information and Cramér-Rao lower bound are also derived. In the Bayesian context, assuming an inverted gamma prior on δ, the uniqueness, boundedness and asymptotics of the highest posterior density estimator of δ can be deduced in a similar way. Finally, an illustrative example is included.     

Resistance to metropolitan institutionality and planning in Chile

In this article, the authors review and analyse two key processes conducted by the Chilean state over the past 50 years. The first process consists of the development of specific planning instruments for the particular realities of metropolitan areas. The second process consists of the successive legislative attempts to work towards a definition of a new form of institutionality for cities with metropolitan profiles. These attempts have either failed or solely become bills of law. Both processes suggest a political and technical resistance throughout history, to substantially modify institutionality, as well as planning instruments, in order to make them more appropriate and consistent with the needs of growing metropolitan areas in Chile.     

Accuracy of approximate progressively censored reliability sampling plans for exponential models

Reliability sampling plans provide an efficient method to determine the acceptability of a product based upon the lifelengths of some test units. Usually, they depend on the producer and consumer’s quality requirements and do not admit closed form solutions. Acceptance sampling plans for one- and two-parameter exponential lifetime models, derived by approximating the operating characteristic curve, are presented in this paper. The accuracy of these approximate plans, which are explicitly expressible and valid for failure and progressive censoring, is assessed. The approximation proposed in the one-parameter case is found to be practically exact. Explicit lower and upper bounds on the smallest sample size are given in the two-parameter case. Some additional advantages are also pointed out.     

On the Construction of Families of Absolutely Continuous Copulas with Given Restrictions

ABSTRACT

We prove that the standard EWMA mean chart with asymptotic control limits and the EWMA mean chart with time-varying control limits for monitoring mean changes in a normal process with known mean and known variance are ARL-unbiased. Using the results derived we discuss the effects of estimation of the process mean on ARL.     

Improving citizens’ online engagement via community managers: an explanatory study

The role of community manager is gaining importance as the proper usage of social media becomes a key factor for achieving more active involvement of citizens in social and political issues. Focused on Spanish local governments and in line with the literature of Excellence Theory, this paper aims to analyze whether some characteristics of the community manager function are determinant in their fostering of citizens’ online engagement via social media. In particular ‘independence’, ‘having access to the dominant coalition’, ‘gender diversity’, ‘continuous training’ and ‘culture of the organization’ are the characteristics considered in this paper. As to the main findings, this study confirms that community managers have not as yet achieved their goal of embedding the use of social media by citizens as a means of establishing more direct contact with their local governments. Moreover, in line with Excellence Theory, community managers of local governments should be aware of the importance of having direct access to key managers of the organization in order to better achieve the objectives of the organization and, more specifically, to increase citizens’ engagement. Furthermore, continuous training in issues related to social media truly helps develop the skills and potential of community managers. Likewise, an excellent communication department should rely on good professionals no matter their gender, and, in this sense, the gender of community managers is not a significant factor in their performance. However, the results of this study also reveal that in the case of public sector community managers, an authoritarian culture seems to be a determining factor for obtaining better results in enhancing citizens’ engagement.     

LAN property for an ergodic diffusion with jumps

In this paper, we consider a multidimensional ergodic diffusion with jumps driven by a Brownian motion and a Poisson random measure associated with a compound Poisson process, whose drift coefficient depends on an unknown parameter. Considering the process discretely observed at high frequency, we derive the local asymptotic normality (LAN) property.     

True Versus Spurious Long Memory: Some Theoretical Results and a Monte Carlo Comparison

A common feature of financial time series is their strong persistence. Yet, long memory may just be the spurious effect of either structural breaks or slow switching regimes. We explore the effects of spurious long memory on the elasticity of the stock market price with respect to volatility and show how cross-sectional aggregation may generate spurious persistence in the data. We undertake an extensive Monte Carlo study to compare the performance of five tests, constructed under the null of true long memory versus the alternative of spurious long memory due to level shifts or breaks.     

Your work may be killing you! Workaholism,sleep problems and cardiovascular risk

This study tests the relationships between workaholism (i.e. working excessively and compulsively), sleep problems and cardiovascular risk in 537 employees from five Spanish hospitals. Four types of worker (i.e. workaholics, positive workers, compulsive workers and hard workers) were distinguished, and their health indicators were compared. The results showed that workaholics experienced significantly more sleep problems (i.e. morning tiredness, sleeping while driving and sleeping fewer hours both on weekdays and at weekends, with poorer quality), had higher relative risk scores, and consumed more caffeine and alcohol than the other patterns of worker (positive, compulsive and hard workers). Further analyses revealed that sleep problems fully mediated the relationship between workaholism (i.e. working excessively and compulsively) and cardiovascular risk. The study emphasizes the fact that being a workaholic might be a significant risk factor for having sleep problems and cardiovascular disease.     

Retirement Planning Among Hispanics: In God’s Hands?

We conducted a qualitative study on retirement preparedness among middle-aged and older low-income Hispanics in Los Angeles. Data were derived from four focus groups conducted in the greater Los Angeles area. Findings demonstrate how behavioral and cultural factors—family experiences, religiosity, and denial of retirement—explain the lack of savings and preparedness for retirement. Findings also indicate that the majority of participants want to be economically independent and to keep working until they are unable to do so. Participants helped their parents financially but did not feel comfortable asking their own children for help. Instead, participants placed their survival in retirement “in God’s hands.”