Simultaneous marginal survival estimators when doubly censored data is present

A doubly censoring scheme occurs when the lifetimes T being measured, from a well-known time origin, are exactly observed within a window [L, R] of observational time and are otherwise censored either from above (right-censored observations) or below (left-censored observations). Sample data consists on the pairs (U, δ) where U = min{R, max{T, L}} and δ indicates whether T is exactly observed (δ = 0), right-censored (δ = 1) or left-censored (δ = −1). We are interested in the estimation of the marginal behaviour of the three random variables T, L and R based on the observed pairs (U, δ). We propose new nonparametric simultaneous marginal estimators [^(S)]_T, [^(S)]_L{\hat S_{T}, \hat S_{L}} and [^(S)]_R{\hat S_{R}} for the survival functions of T, L and R, respectively, by means of an inverse-probability-of-censoring approach. The proposed estimators [^(S)]_T, [^(S)]_L{\hat S_{T}, \hat S_{L}} and [^(S)]_R{\hat S_{R}} are not computationally intensive, generalize the empirical survival estimator and reduce to the Kaplan-Meier estimator in the absence of left-censored data. Furthermore, [^(S)]_T{\hat S_{T}} is equivalent to a self-consistent estimator, is uniformly strongly consistent and asymptotically normal. The method is illustrated with data from a cohort of drug users recruited in a detoxification program in Badalona (Spain). For these data we estimate the survival function for the elapsed time from starting IV-drugs to AIDS diagnosis, as well as the potential follow-up time. A simulation study is discussed to assess the performance of the three survival estimators for moderate sample sizes and different censoring levels.     

Unanticipated Educational Consequences of a Positive Parent‐Child Relationship

If today there exists a single transcendent idea about the family‐school connection, it is that a positive parent‐child relationship improves children's chances of succeeding in school. However, using data from the Texas Higher Education Opportunity Project (N = 5,836), we demonstrate that, although positive parent‐child relations are associated with better academic achievement in high school, they also are associated with an increased desire to live at home during college, which in turn decreases students' chances of enrolling in a 4‐year college. Furthermore, we replicated some of these associations using the National Longitudinal Study of Adolescent Health (N = 10,120), demonstrating that positive family dynamics can influence educational outcomes in potentially divergent and unanticipated directions.     

Age of Onset in Pathological Gambling: Clinical,Therapeutic and Personality Correlates

We aimed to explore the association between age of onset of gambling problems and current psychopathological and clinical status, personality profile and therapeutic outcome in a sample of pathological gamblers. A total of 904 consecutive pathological gambling patients were administered several instruments about gambling behavior, psychopathology and personality. They received a 4-month cognitive-behavioral group treatment. Information of dropouts and relapses during treatment was registered. Older age of onset of gambling problems was associated with higher general psychopathology (SCL-90-R Paranoid Ideation, Psychoticism, Depression; P < 0.015). Younger age of onset was related to greater severity of pathological gambling (P < 0.015), higher novelty seeking, and lower self-directedness (P < 0.015). No statistically significant association was found between age of onset and relapse and dropouts during treatment. Age of onset of gambling problems seems to influence the clinical presentation of pathological gambling but not treatment outcome.     

Mortality and economic fluctuations

Using wavelet methods, this paper analyzes the relationship between the age-adjusted, infant, and cause-specific mortality rates and the business cycle in Sweden over the period 1800–2000 (1911–1996 for cause-specific mortality). For the period 1800–2000, an increase in GDP by 1% decreased mortality by 0.7%. This overall relationship is due to a strong counter-cyclical relationship in the nineteenth century, which disappeared in the twentieth century. In contrast, in the twentieth century higher mortality in economic upturns is found for mortality caused by circulatory diseases (including stroke) and accidents.     

An empirical comparison of Canonical Correspondence Analysis and STATICO in the identification of spatio-temporal ecological relationships

The wide-ranging and rapidly evolving nature of ecological studies mean that it is not possible to cover all existing and emerging techniques for analyzing multivariate data. However, two important methods enticed many followers: the Canonical Correspondence Analysis (CCA) and the STATICO analysis. Despite the particular characteristics of each, they have similarities and differences, which when analyzed properly, can, together, provide important complementary results to those that are usually exploited by researchers. If on one hand, the use of CCA is completely generalized and implemented, solving many problems formulated by ecologists, on the other hand, this method has some weaknesses mainly caused by the imposition of the number of variables that is required to be applied (much higher in comparison with samples). Also, the STATICO method has no such restrictions, but requires that the number of variables (species or environment) is the same in each time or space. Yet, the STATICO method presents information that can be more detailed since it allows visualizing the variability within groups (either in time or space). In this study, the data needed for implementing these methods are sketched, as well as the comparison is made showing the advantages and disadvantages of each method. The treated ecological data are a sequence of pairs of ecological tables, where species abundances and environmental variables are measured at different, specified locations, over the course of time.     

Emotions and the optimality of uneven tournaments

Standard results from tournament theory show that an employer should avoid organizing uneven tournaments in which workers are characterized by different cost functions. In this paper, we introduce a concept of emotions that workers have when comparing their own performance with the performances of their co-workers. We can show that under emotional workers the employer may prefer uneven tournaments to even ones. In that case, the employer benefits from both positive and negative emotions. Moreover, the behavior of emotional workers fits well with experimental findings on uneven tournaments where players choose excessive effort levels.     

Bimodality based on the generalized skew-normal distribution

This paper focuses on the development of a new extension of the generalized skew-normal distribution introduced in Gómez et al. [Generalized skew-normal models: properties and inference. Statistics. 2006;40(6):495–505]. To produce the generalization a new parameter is introduced, the signal of which has the flexibility of yielding unimodal as well as bimodal distributions. We study its properties, derive a stochastic representation and state some expressions that facilitate moments derivation. Maximum likelihood is implemented via the EM algorithm which is based on the stochastic representation derived. We show that the Fisher information matrix is singular and discuss ways of getting round this problem. An illustration using real data reveals that the model can capture well special data features such as bimodality and asymmetry.     

Modified slashed-Rayleigh distribution

A new family of slash distributions, the modified slashed-Rayleigh distribution, is proposed and studied. This family is an extension of the ordinary Rayleigh distribution, being more flexible in terms of distributional kurtosis. It arises as a quotient of two independent random variables, one being a Rayleigh distribution in the numerator and the other a power of the exponential distribution in denominator. We present properties of the proposed family. In addition, we carry out estimation of the model parameters by moment and maximum likelihood methods. Finally, we conduct a small-scale simulation study to evaluate the performance of the maximum likelihood estimators and apply the results to a real data set, revealing its good performance.