The beta modified Weibull distribution

A five-parameter distribution so-called the beta modified Weibull distribution is defined and studied. The new distribution contains, as special submodels, several important distributions discussed in the literature, such as the generalized modified Weibull, beta Weibull, exponentiated Weibull, beta exponential, modified Weibull and Weibull distributions, among others. The new distribution can be used effectively in the analysis of survival data since it accommodates monotone, unimodal and bathtub-shaped hazard functions. We derive the moments and examine the order statistics and their moments. We propose the method of maximum likelihood for estimating the model parameters and obtain the observed information matrix. A real data set is used to illustrate the importance and flexibility of the new distribution.     

How obstetricians and pregnant women decide mode of birth in light of a recent regulation in Brazil

Background

In Brazil, 88% of births among women with private insurance are caesarean sections, even though a caesarean rate above 15% is associated with greater maternal and child morbidity and mortality. Aiming to reduce unnecessary caesarean sections in the private sector, in July 2015 the Brazilian government enacted Resolução Normativa 368, a regulation requiring the use of partograms, pre-natal cards to document pregnancies, and consent forms for elective caesareans, and recommending that obstetricians provide women with an informational letter about birth.

Liminal Stigma and Disaligning Activity: Online Comments about Trump's Family Separation Policy

In 2018, the Trump administration initiated a “zero-tolerance” border policy wherein they criminally prosecuted all individuals who were apprehended crossing the border without proper authorization. The policy change resulted in numerous migrant children being separated from their parents. Through a qualitative content analysis of 1500 YouTube comments made in response to CNN and ProPublica news coverage, we examine each side's aligning activity. Separation challengers claimed border crossers were innocent while condemning their opponents as racist, cruel, and otherwise shameful. Separation advocates bolstered their own claims of innocence by denying that the detainees are victims and condemning separation challengers as hypocrites, dishonest, complicit in illegal immigration, and generally loathsome. These findings show that, enabled by social media, aligning activity in stigma contests can produce a liminal stigma, where identities suffer the ideational aspects of stigma but not necessarily the loss of social status.     

The new Neyman type A generalized odd log-logistic-G-family with cure fraction

The work proposes a new family of survival models called the Odd log-logistic generalized Neyman type A long-term. We consider different activation schemes in which the number of factors M has the Neyman type A distribution and the time of occurrence of an event follows the odd log-logistic generalized family. The parameters are estimated by the classical and Bayesian methods. We investigate the mean estimates, biases, and root mean square errors in different activation schemes using Monte Carlo simulations. The residual analysis via the frequentist approach is used to verify the model assumptions. We illustrate the applicability of the proposed model for patients with gastric adenocarcinoma. The choice of the adenocarcinoma data is because the disease is responsible for most cases of stomach tumors. The estimated cured proportion of patients under chemoradiotherapy is higher compared to patients undergoing only surgery. The estimated hazard function for the chemoradiotherapy level tends to decrease when the time increases. More information about the data is addressed in the application section.     

Bayesian estimation of a flexible bifactor generalized partial credit model to survey data

Item response theory (IRT) models provide an important contribution in the analysis of polytomous items, such as Likert scale items in survey data. We propose a bifactor generalized partial credit model (bifac-GPC model) with flexible link functions - probit, logit and complementary log-log - for use in analysis of ordered polytomous item scale data. In order to estimate the parameters of the proposed model, we use a Bayesian approach through the NUTS algorithm and show the advantages of implementing IRT models through the Stan language. We present an application to marketing scale data. Specifically, we apply the model to a dataset of non-users of a mobile banking service in order to highlight the advantages of this model. The results show important managerial implications resulting from consumer perceptions. We provide a discussion of the methodology for this type of data and extensions. Codes are available for practitioners and researchers to replicate the application.     

Peers Increase Late Adolescents' Exploratory Behavior and Sensitivity to Positive and Negative Feedback

Adolescents take more risks with peers than when alone. It is not clear how peer presence affects adolescents' risky decision making, however. We used the Iowa Gambling Task (IGT)—a game used to assess decision making involving risk and reward—to examine how peers affect late adolescents' exploration of relevant environmental cues, ability to learn from the outcomes (positive and negative) of that exploration, and ability to integrate feedback to adjust behavior toward optimal long‐term outcomes. One hundred and one 18‐ to 22‐year old males (M = 19.8 years) were randomly assigned to play the IGT either alone or observed by peers. Late adolescents tested with observers engaged in more exploratory behavior, learned faster from both positive and negative outcomes, and evinced better task performance than those tested alone.     

Unity and fragmentation of the habitus

This paper examines a unitary notion of the habitus present in Bourdieu's early works and its transformation along his sociological career, to later conceptions of a fragmented habitus concept to examine contemporary relationality and social change. The career of the concept of habitus in Bourdieu shows that interplays of habitus and fields are seen to demand increasing labour of integration from individuals as social life becomes more differentiated. The paper claims the need for sociology to engage with field analyses to advance explorations of the habitus and to acknowledge the potential pliability of the concept. It is suggested that sociology may adopt the psychoanalytic notion of ‘standing in spaces’ (and associated notions of ‘liminality’ and experiences in interstitial positons) for a productive development of the notion of fragmented habitus, and to enhance proposals that view the social with a history that is made available to humans to change.     

The Persistence of the slave market in seventeenth-century Central Mexico

This study, based on an extensive notarial database, demonstrates the significance of slavery in Central Mexico during the seventeenth century. Thousands of bills of sale from Mexico City and Puebla – the largest and most lucrative slave markets in the region – show that the slave trade did not collapse with the end of the Portuguese asiento in 1640. A growing population of American-born creoles sustained the market during the subsequent decades, along with a modest number of new African arrivals. In 1700, slavery remained integral to Central Mexico's economy.