A review of the CTP distribution: a comparison with other over- and underdispersed count data models

The complex triparametric Pearson (CTP) distribution is a flexible model belonging to the Gaussian hypergeometric family that can account for over- and underdispersion. However, despite its good properties, not much attention has been paid to it. So, we revive the CTP comparing it with some well-known distributions that cope with overdispersion (negative binomial, generalized Poisson and univariate generalized Waring) as well as underdispersion (Conway–Maxwell–Poisson (CMP) and hyper-Poisson (HP)). We make a simulation study that reveals the performance of the CTP and shows that it has its own space among count data models. In this sense, we also explore some overdispersed datasets which seem to be more appropriately modelled by the CTP than by other usual models. Moreover, we include two underdispersed examples to illustrate that the CTP can provide similar fits to the CMP or HP (sometimes even more accurate) without the computational problems of these models.     

Variance Inflation Factor and Condition Number in multiple linear regression

The Variance Inflation Factor and the Condition Number are measures traditionally applied to detect the presence of collinearity in a multiple linear model. This paper presents the relation and the difference between both measures from theoretical and empirical perspectives by using Monte Carlo simulations and taking special interest in the computational techniques.     

Degradation modeling based on gamma process models with random effects

The random effects in a gamma process are introduced in terms of its scale parameter. However, the scale parameter affects both its mean and variance. Hence, the variation of the degradation rates and the within degradation increments are expected to be large. For some products, the random effects affect just the rate or just the volatility of the process. Thus, two modifications of the parameters' structure of the gamma process are proposed. One implies that the random effects affect just the volatility and the second just the rate. A Bayesian estimation approach is provided and implemented in two case studies.     

The variance upper bound for a mixed random variable

In this note, we derive upper bounds on the variance of a mixed random variable. Our results are an extension of previous results for unimodal and symmetric random variables. The novelty of our findings is that this mixed random variable does not necessarily need to be symmetric and is multimodal. We also characterize the cases when these bounds are optimal.     

Organizational Learning Capability and Job Satisfaction: an Empirical Assessment in the Ceramic Tile Industry*

Organizational learning capability has been considered an essential issue of an organization's effectiveness and potential to innovate and grow. Although its positive effects on organizations and employees are generally assumed, there is no empirical evidence of its positive association with employee attitudes such as job satisfaction. This paper aims to investigate the relationship between organizational learning capability and job satisfaction through the questionnaire responses of 157 employees from eight companies in the Spanish ceramic tile industry. Results suggest that organizational learning capability and job satisfaction are strongly linked.     

Osteoporosis, falls and exercise

Osteoporosis, a manifestation of bone atrophy that leads to great susceptibility to fractures, is a very important public health problem today because of its great morbidity, mortality and important economic repercussions. It is a problem that will tend to become more serious with the increase in the number of elderly persons. Bone mass is gained during adolescence, reaches a plateau during the third decade and remains stable until approximately age 50, after which a progressively gradual loss is observed. There is no real cure for osteoporosis, but a series of strategies can be used to reduce bone loss and improve bone mass. Osteoporosis has been considered a disease that accompanies the process of ageing; however, this fatalistic attitude should be discarded, as it is possible to correct and decrease the risk factors. Intervention strategies are based on three pillars: nutrition, physical activity and pharmacological agents. Physical activities and exercise programmes are important because they not only can counter the loss of bone mass but also improve neuromuscular capacity, maintaining and increasing strength and muscle mass, which can help to avoid falls and reduce their impact and consequences. The general principles that apply to any exercise programme also apply to preventing bone mass loss. They also can be applied to persons with osteoporosis. However, to understand the peculiarities of these programmes, the propensity for suffering fractures of these former groups should be kept in mind. Special care should be taken to avoid falls and injuries. Weight-bearing exercise and resistance training are recommended for the prevention programmes. Other activities such as tai-chi, dancing, gymnastic or callisthenic exercises can help to improve balance, gait and muscle coordination and diminish the risk of falling. These programmes should be complemented with postural education and a series of safety precautions.     

Further properties of generalized residual designs

The concept of ‘residuation’ is extended so that all ‘generalized residual designs’ (in the sense of Shrinkhande and Singhi) are in fact ‘residual’ with respect to the extended type of residuation. A measure of departure from the usual type of residuation is given in general, and stronger estimates of this measure are given for affine designs.     

Childhood sexual experiences and the perception of abuse among Latino men who have sex with men

There is a lack of consensus on how to define childhood sexual abuse (CSA). In this study we explore the perceptions of CSA among men who had such experiences. One hundred Latino men (predominately gay) who had childhood sexual experiences with an older partner (CSEOP) were asked whether they considered their experiences sexual abuse (41 said no; 59 said yes). Those who felt abused were younger when the events happened and were more likely to have been physically forced, physically hurt, threatened, and emotionally hurt. Negative correlates of CSEOP in adulthood were also explored. Men who considered themselves the victims of CSA differed from those without CSEOP in having more alcohol use, unprotected anal sex, and male sex partners.     

The economy of risk and respect: accounts by Puerto Rican sex workers of HIV risk taking

Three-hundred-eleven female drug-using sex workers in urban Puerto Rico were asked to describe their last negotiation with a client. They described efforts to protect themselves from many hazards of sex work, including violence, illness, and drug withdrawal. They also described efforts to minimize the stigma and marginalization of sex work by cultivating relationships with clients, distinguishing between types of clients, and prioritizing their role as mothers. Sex workers adopted alternating gender roles to leverage autonomy and respect from clients. Their narratives suggest that sex workers negotiate a world in which HIV is relative to other risks, and in which sexual practices which are incomprehensible from an HIV-prevention perspective are actually rooted in a local cultural logic. Future HIV prevention efforts should frame condom use and other self-protective acts in terms that build upon sex workers own strategies for understanding their options and modifying their risks.