Bayesian robustness of the compound Poisson distribution under bidimensional prior: an application to the collective risk model

The distribution of the aggregate claims in one year plays an important role in Actuarial Statistics for computing, for example, insurance premiums when both the number and size of the claims must be implemented into the model. When the number of claims follows a Poisson distribution the aggregated distribution is called the compound Poisson distribution. In this article we assume that the claim size follows an exponential distribution and later we make an extensive study of this model by assuming a bidimensional prior distribution for the parameters of the Poisson and exponential distribution with marginal gamma. This study carries us to obtain expressions for net premiums, marginal and posterior distributions in terms of some well-known special functions used in statistics. Later, a Bayesian robustness study of this model is made. Bayesian robustness on bidimensional models was deeply treated in the 1990s, producing numerous results, but few applications dealing with this problem can be found in the literature.     

Activism among older women in Quebec, Canada: changing the world after age 65

The aim of this article is to examine senior women's involvement experience in Quebec, Canada. Study results are based on a qualitative methodology, and shed light on family history and continuity in the involvement trajectory, diversity in terms of group type and involvement practices, and gender differences in involvement. The meaning that older women attribute to their involvement is also addressed, including attitudes toward feminism. The discussion highlights the extent to which older women's involvement has been marked by their life trajectories, above and beyond their age. In sum, their involvement in the private and public spheres is quite impressive.     

Evaluating school and parent reports of the national student achievement testing system (SIMCE) in Chile: Access,comprehension, and use

This evaluation examined school and parent reports of the national student achievement testing system (SIMCE) in Chile regarding three dimensions: access, comprehension, and use. We conducted phone surveys with a representative sample of directors (N = 375), teachers (N = 1145) and parents (N = 625), and we collected more in-depth data through interviews and focus groups in 16 of these schools. The results indicate that access to the reports is not an obstacle to use for school actors, but it is for parents. While summative ratings of the reports in terms of their clarity and utility were generally very positive, the actual recall and interpretation of even basic information (assessed through case scenarios) was incorrect for a majority of teachers and parents, and reported uses of the information were both intended and unintended in nature. We also found some statistically significant differences regarding comprehension and use among subgroups of our sample. Our findings are especially relevant given the expectations attached to the use of the reports for school improvement on the one hand, and parents’ behavior as critical consumers of education on the other hand.     

Determinants of in-group bias: Is group affiliation mediated by guilt-aversion?

In-group favoritism in social dilemma situations is one of Social Identity Theory’s main findings. We investigate what causes the in-group bias: is it merely due to group affiliation or, alternatively, is guilt-aversion moderating the strength of in-group favoring? We induce group membership in a minimal group setting, observe in-/out-group transfers and elicit corresponding beliefs. According to our experimental data group affiliation affects beliefs and explains a substantial part of the bias. Evidence for guilt-aversion is found only when beliefs are elicited before actions.     

Children’s Strategies for Agency in Preschool

This article is based on an ethnographic study of children’s everyday life in Swedish preschools. The ethnography is used to explore children’s strategies for influencing, defending and constructing the social order of a preschool institution. The focus of our concern is on how the children, in their interactions with each other and with the preschool teachers, manage the collective regulation and how they negotiate their participation in collective activities. There is an inherent tension between free play and the high degree of routinised and collective activities within the preschool institution. The study shows that children are active in playing at the border, acting as if the institution is the children’s place. It also shows how they draw on different strategies as resources for managing the regulations, accounting for personal autonomy and negotiating the social order. In taking a child perspective and acknowledging children as active agents, it is possible to see how they influence and shape their everyday life in a preschool context. In addition, the article illustrates individual children’s strategic and pragmatic use of resources and in doing so contribute to their own childhood and thereby become part of a social and cultural construction process.     

Number of children and later-life mortality among Finns born 1938–50

We investigated the association between number of offspring and later-life mortality of Finnish men and women born 1938–50, and whether the association was explained by living conditions in own childhood and adulthood, chronic conditions, fertility timing, and unobserved characteristics common to siblings. We used a longitudinal 1950 census sample to estimate mortality at ages 50–72. Relative to parents of two children, all-cause mortality is highest among childless men and women, and elevated among those with one child, independently of observed confounders. Fixed-effect models, which control for unobserved characteristics shared by siblings, clearly support these findings among men. Cardiovascular mortality is higher among men with no, one, or at least four children than among those with two. Living conditions in adulthood contribute to the association between the number of children and mortality to a greater extent than childhood background, and chronic conditions contribute to the excess mortality of the childless.     

Measuring disparities in access to water based on the normative content of the human right

Measuring access to water in the Sustainable Development Goals era involves taking into account the human rights framework. Therefore, its content should be considered to conceptualize the level of service through adequate indicators and to follow-up inequities reduction at global, national and local level. This research develops and tests a methodology to measure intra-community disparities based on human right to water normative criteria through a stratified sampling, splitting households served by community based organizations and those self-provided. This approach implies considering much reduced populations, thus special care needs to be taken with sample sizes and uncertainty of estimators. The proposed methodology is practical to locate and accurately characterize minority sectors within rural communities and allows moving beyond central-tendency estimators. It implies higher costs for field data collection than traditional approaches, but this can be assumed given the relevance of the approach from a human rights perspective, which calls for adequate tools for equity-oriented policy making at local level. The research point out how results might be used to shape decision-making processes.     

On the computation of the noncentral <Emphasis Type="Italic">F</Emphasis> and noncentral beta distribution

Unfortunately many of the numerous algorithms for computing the comulative distribution function (cdf) and noncentrality parameter of the noncentral F and beta distributions can produce completely incorrect results as demonstrated in the paper by examples. Existing algorithms are scrutinized and those parts that involve numerical difficulties are identified. As a result, a pseudo code is presented in which all the known numerical problems are resolved. This pseudo code can be easily implemented in programming language C or FORTRAN without understanding the complicated mathematical background. Symbolic evaluation of a finite and closed formula is proposed to compute exact cdf values. This approach makes it possible to check quickly and reliably the values returned by professional statistical packages over an extraordinarily wide parameter range without any programming knowledge. This research was motivated by the fact that a very useful table for calculating the size of detectable effects for ANOVA tables contains suspect values in the region of large noncentrality parameter values compared to the values obtained by Patnaik’s 2-moment central-F approximation. The cause is identified and the corrected form of the table for ANOVA purposes is given. The accuracy of the approximations to the noncentral-F distribution is also discussed. The authors wish to thank Mr. Richárd Király for his preliminary work. The authors are grateful to the Editor and Associate Editor of STCO and the unknown reviewers for their helpful suggestions.     

Early Segmentation Abilities in Preterm Infants

Infants born preterm have higher risks of developing linguistic deficits. Considering that the ability to segment words from fluent speech is crucial for lexical acquisition, Experiment 1 tested the ability of healthy extremely‐to‐late preterm infants to segment monosyllabic words at 6 months of postnatal age. Results establish basic segmentation skills in these infants. While we failed to find an effect of the degree of prematurity, this issue will need further exploration. Future studies will also have to specify the scope of these early segmentation skills, both in terms of the types of words segmented, the cues used to do so, and in terms of possible differences in performance between subgroups of preterm infants (e.g., based on gestational age or medical risks). Lastly, given that the preterm infants tested had a mean maturational age of 4 months, Experiment 2 explored monosyllabic segmentation in full‐term 4‐month olds. Infants succeeded at the task, providing the earliest developmental evidence of word segmentation in full‐term infants. These findings better specify the early trajectory of segmentation abilities in both full‐term and healthy, low‐risk preterm infants and support the proposal that prematurity might have a differential effect on the early acquisition of various linguistic levels.     

Evidence that Two‐Year‐Old Children are Sensitive to Information Presented in Arguments

Preschoolers are more likely to endorse testimony supported by strong arguments than by weak, circular ones. Two‐year‐olds exchange arguments with others, but no experiment has demonstrated that they are sensitive to information presented as argument. In the first phase of this study, 2‐year‐olds were shown ambiguous pictures—for instance a bird–fish hybrid—and asked what they thought the picture represented. An informant then contradicted them, providing either a strong argument, a circular argument, or no argument, and the children were asked what they now thought the hybrid was. The second phase was identical to the first, with new hybrids, except that the informant never provided any argument for her position. Finally, in the third phase, the informant left the room and the children were asked again to tell what the hybrids from the first two phases were. On the whole, there was an effect of the amount of information provided in the argument so that children were more likely to endorse labels provided by the informant who had supported her answer with a strong argument in the first phase. Moreover, they generalized the trust granted to informants who provided strong arguments. These results constitute the first experimental demonstration that 2‐year‐olds possess some argument evaluation skills.