A note on replacement policy comparisons from NBUC lifetime of the unit

Age and block replacement policies are commonly used in order to reduce the number of in-service failures when the systems are functioning indefinitely. In reliability theory, the lifetime of a system can be modeled by means of the NBUC aging class that is characterized throughout comparisons of the residual lives in the sense of the icx order. The purpose of this paper is to establish stochastic comparisons between the age (block) replacement policy and a renewal process with no planned replacements when the lifetime of the unit is NBUC. Supported by Ministerio de Ciencia y Tecnología under grant BFM2000-0362     

Constructing the digital patient: Patient organizations and the development of health websites

In order to understand the constraints and challenges of realizing the democratic potentials of the Internet, this paper focuses on the attempts of three Dutch patient organizations to develop health websites. The authors describe how these patient organizations had to overcome specific barriers to develop their digital services. All three organizations faced certain constraints that had negative consequences for the plans they wanted to realize. Lack of financial resources and manpower were the main reasons why these patient organizations could not develop interactive parts of their website or provide personal advice services. Other barriers the patient organizations had to overcome were getting access to digital expertise to build the websites. The paper shows that the development of a website is a very demanding task, even for patient organizations that have in-house expertise with computers and Internet. Moreover, the paper shows that patient organizations do not consider the involvement of patients as crucial for the design of health websites. This research thus confirms previous research findings that users, in this case patients, are largely absent from the design process of information and communication technologies Finally, the paper shows how patient organizations' websites contribute to a redefinition of the patient from being a passive actor towards one who is an active participant in his or her care.     

Formulating waste management strategies based on waste management practices of households in Santiago de Cuba, Cuba

Rapid urbanisation, population growth and changes in lifestyles in low- and middle-income countries contribute to increasing the per capita domestic waste generation. This trend leads to deplorable environmental and public health conditions, especially in rapidly expanding cities of low- and middle-income countries lacking appropriate waste management systems, Santiago de Cuba is no exception. To improve solid waste management in the city of Santiago de Cuba, the generation of household waste was studied and individual waste treatment approaches were assessed. The principle of a household level analysis was adopted to enable the development of strategies based on the specific conditions of households, their awareness and needs.In February 2004, a survey covering 1180 households was conducted on issues such as monthly consumed goods, waste generated and its treatment. The waste generated by the households was subsequently assessed by means of a measuring campaign. The measured volume not only comprised the collected waste fraction but also the waste materials treated on-site or recovered and recycled by all the different means available.The paper contains the results of the composition and distribution of the waste generated by the households as a function of socio-demographic data. Furthermore, the paper describes the various household treatment strategies dependent on specific waste material types. Several types of household waste can be differentiated by statistical cluster analysis. These household types are characterised not only by the amount of waste generated but also by socio-economic status and waste treatment practices. The results obtained are used to develop a range of waste management strategies, each relating to a household type and characterised by its generated amount, waste material type and spatial urban distribution. Since the strategies are adapted to the requirements and needs of the households, they are more readily accepted by the population concerned. Such socially anchored strategies will contribute to improving the waste situation in the city of Santiago de Cuba and allow an optimised allocation of local resources.     

Los determinantes y consecuencias de la desconfianza en México1

This paper analyzes the relationship between interpersonal trust and the trust in different institutions as well as its involvement with sociodemographic and political culture-related variables and its connection with associativism. For this, 1993 and 2000 national surveys where used. The results show that there is independence between interpersonal trust and the trust in institutions, because they are built by different processes. There is also a slight relationship between sociodemographic variables and political values or ideology. Interpersonal trust is linked with active participation in associations, which may point out that it is associated to specific forms of social organization. On the other hand, trust in institutions seems to respond more to the behavior of the political system, its performance, and how it is evaluated. Besides, it appears that the trust is influenced by age or place of residence. Older persons and those living in small villages are associated with conservatism. Non-political institutions (such as religion, unions, etc.) could be affected by policy performance.     

Robust Bayesian bonus-malus premiums under the conditional specification model

The conditional specification technique introduced by Arnold et al. (Conditional specification of statistical models. Springer series in statistics. Springer, New York, 1999) was used in Sarabia et al. (Astin Bull 34(1):85–98, 2004) to obtain bonus-malus premiums. The Poisson distribution for which the parameter is a function of the classical structure parameter was used and a new class of prior distributions appeared in a natural way. This model contains, as a particular case, the classical compound Poisson model. In the present paper, the Bayesian robustness of this new model is examined and found to be much more robust than in the classical model in Gómez et al. (Insur Math Econ 31:105–113, 2002). For the present study, the moment conditions on the prior distribution are required. Examples, with real data, are given to illustrate our ideas under the net and exponential premium principles.     

Small-sample comparisons for powerdivergence goodness-of-fit statistics for symmetric and skewed simple null hypotheses

Power-divergence goodness-of-fit statistics have asymptotically a chi-squared distribution. Asymptotic results may not apply in small-sample situations, and the exact significance of a goodness-of-fit statistic may potentially be over- or under-stated by the asymptotic distribution. Several correction terms have been proposed to improve the accuracy of the asymptotic distribution, but their performance has only been studied for the equiprobable case. We extend that research to skewed hypotheses. Results are presented for one-way multinomials involving k = 2 to 6 cells with sample sizes N = 20, 40, 60, 80 and 100 and nominal test sizes f = 0.1, 0.05, 0.01 and 0.001. Six power-divergence goodness-of-fit statistics were investigated, and five correction terms were included in the study. Our results show that skewness itself does not affect the accuracy of the asymptotic approximation, which depends only on the magnitude of the smallest expected frequency (whether this comes from a small sample with the equiprobable hypothesis or a large sample with a skewed hypothesis). Throughout the conditions of the study, the accuracy of the asymptotic distribution seems to be optimal for Pearson's X² statistic (the power-divergence statistic of index u = 1) when k > 3 and the smallest expected frequency is as low as between 0.1 and 1.5 (depending on the particular k, N and nominal test size), but a computationally inexpensive improvement can be obtained in these cases by using a moment-corrected h² distribution. If the smallest expected frequency is even smaller, a normal correction yields accurate tests through the log-likelihood-ratio statistic G² (the power-divergence statistic of index u = 0).     

Bayesian inference for the mean and standard deviation of a normal population when only the sample size,mean and range are observed

Consider a random sample X₁, X₂,…, X_n, from a normal population with unknown mean and standard deviation. Only the sample size, mean and range are recorded and it is necessary to estimate the unknown population mean and standard deviation. In this paper the estimation of the mean and standard deviation is made from a Bayesian perspective by using a Markov Chain Monte Carlo (MCMC) algorithm to simulate samples from the intractable joint posterior distribution of the mean and standard deviation. The proposed methodology is applied to simulated and real data. The real data refers to the sugar content (^oBRIX level) of orange juice produced in different countries.     

Rao distance as a measure of influence in the multivariate linear model

Several methods have been suggested to detect influential observations in the linear regression model and a number of them have been extended for the multivariate regression model. In this article we consider the multivariate general linear model, Y = XB + k , which contains the linear regression model and the multivariate regression model as particular cases. Assuming that the random disturbances are normally distributed, the BLUE of v B is also normally distributed. Since the distribution of the BLUE of v B and the distribution of the BLUE of v B in the model with the omission of a set of observations differ, to study the influence that a set of observations has on the BLUE of v B , we propose to measure the distance between both distributions. To do this we use Rao distance.     

Minimum Φ-divergence estimator in logistic regression models

A general class of minimum distance estimators for logistic regression models based on the ϕ-divergence measures is introduced: The minimum ϕ-divergence estimator, which is seen to be a generalization of the maximum likelihood estimator. Its asymptotic properties are studied as well as its behaviour in small samples throught a simulation study. This work was supported partially by Grant DGI (BMF2003-00892).