A Sequential Markov Chain Monte Carlo Approach to Set-up Adjustment of a Process over a Set of Lots

We consider the problem of adjusting a machine that manufactures parts in batches or lots and experiences random offsets or shifts whenever a set-up operation takes place between lots. The existing procedures for adjusting set-up errors in a production process over a set of lots are based on the assumption of known process parameters. In practice, these parameters are usually unknown, especially in short-run production. Due to this lack of knowledge, adjustment procedures such as Grubbs' (1954, 1983) rules and discrete integral controllers (also called EWMA controllers) aimed at adjusting for the initial offset in each single lot, are typically used. This paper presents an approach for adjusting the initial machine offset over a set of lots when the process parameters are unknown and are iteratively estimated using Markov Chain Monte Carlo (MCMC). As each observation becomes available, a Gibbs Sampler is run to estimate the parameters of a hierarchical normal means model given the observations up to that point in time. The current lot mean estimate is then used for adjustment. If used over a series of lots, the proposed method allows one eventually to start adjusting the offset before producing the first part in each lot. The method is illustrated with application to two examples reported in the literature. It is shown how the proposed MCMC adjusting procedure can outperform existing rules based on a quadratic off-target criterion.     

Ruptura matrimonial y salud mental: Variables psicosociales asociadas en el caso de la mujer

Resumen

En el trabajo se presentan los resultados de la evaluación de un grupo de mujeres con ruptura matrimonial en dos aspectos que la literatura sobre el tema considera relevantes: vinculación al ex marido y situación emocional. La primera se ba medido mediante el ASD (Kitson, 1982) y la segunda con el CAQ (Krug, 1980). Se ba considerado también la influencia de las variables psicosociales sobre la situación de la mujer divorciada, tales como actividad económica, duración del matrimonio, hijos, nueva pareja… En el caso del CAQ se ha utilizado un grupo control de mujeres casadas. Los resultados muestran que el impacto emocional del divorcio existe puesto que las mujeres con ruptura matrimonial alcanzan puntuaciones más altas que las casadas en las escalas de depresión, paranoidismo y esquizofrenia. En vinculación al ex marido las puntuaciones muestran un adecuado nivel de independencia. Las mujeres que conservan mayor vinculación presentan una situación emocional peor.     

A coordinate-free approach to testable hypotheses

Using the coordinate-free version of the linear model and geometrical considerations, the usual definition of testable hyptheses is extended. The concept of partially testable hypotheses is defined in that context. This new approach provides an alternative to the one given by Peixoto (1986), offering some complementary aspects. Simple and direct techniques for testing the new testable hyptheses by means of the classical testing procedure are given.     

Flora of the tram tracks of Bratislava

Urban Ecosystems - Tram and railway tracks represent specific urban habitats, which host a specific type of flora. This study aims to compile the information about species composition of flora of...     

Multivariate models for correlated count data

In this study, we deal with the problem of overdispersion beyond extra zeros for a collection of counts that can be correlated. Poisson, negative binomial, zero-inflated Poisson and zero-inflated negative binomial distributions have been considered. First, we propose a multivariate count model in which all counts follow the same distribution and are correlated. Then we extend this model in a sense that correlated counts may follow different distributions. To accommodate correlation among counts, we have considered correlated random effects for each individual in the mean structure, thus inducing dependency among common observations to an individual. The method is applied to real data to investigate variation in food resources use in a species of marsupial in a locality of the Brazilian Cerrado biome.     

Gender Segregation in the Spanish Labor Market: An Alternative Approach

The aim of this paper is to study occupational segregation by gender in Spain, which is a country where occupational segregation explains a large part of the gender wage gap. As opposed to previous studies, this paper measures not only overall segregation, but also the segregation of several population subgroups. For this purpose, this paper uses new measures recently proposed by Alonso-Villar and Del Río ( Local versus overall segregation measures, Documento de Traballo 0802, Departamento de Economía Aplicada, Universidade de Vigo, 2008). Moreover, two decompositions of their local segregation curves are proposed, which allows us to go further in the empirical analysis.     

On the potential in the estimation of linear functions in regression

New aspects of potential in Cook's Influence measure for linear combinations are explored. It is shown that this potential can be considered as a case influence measure in the scatter of estimated combinations. The potential is related to precise estimation directions and multicollinearity concepts; It Is also used as a basis for selection of new cases.     

Exploring the specific needs of an understudied group: Children with intellectual disability in residential child care

Children and adolescents who live in out of home care in the child protection system are considered to be vulnerable to manifesting mental health disorders as well as other types of difficulties. This risk is greater in the case of children who display any type of disability. The aim of this study is to profile the state of health and well-being of a group of children presenting intellectual disability who live in residential care in a Spanish autonomous community and to compare these results with their non-disabled peers.