Estimation of weibull location

A simulation study was carried out to compare the performances of two different simple estimators of the location parameter for a three-parameter Weibull distribution Both Estimators have been suggested by recent paper in the literature. Bras and mean square error are examined for many different sample-size and shape-parameter-value combinations. Strong evidence of the domination of one estimator over the other is found.     

Asymptotic behaviour of binned kernel density estimators for locally non-stationary random fields

We investigate the asymptotic behaviour of binned kernel density estimators for dependent and locally non-stationary random fields converging to stationary random fields. We focus on the study of the bias and the asymptotic normality of the estimators. A simulation experiment conducted shows that both the kernel density estimator and the binned kernel density estimator have the same behavior and both estimate accurately the true density when the number of fields increases. We apply our results to the 2002 incidence rates of tuberculosis in the departments of France.     

Changes in anti-fat weight bias in women after exposure to thin and plus-sized models

We examined whether exposing women to female models with different body sizes lead to changes in weight-based attitudes and whether evaluation focus altered the effects. Female college students (N = 214) were exposed to 22 images of either thin or overweight models. Participants rated models on either appearance or non-appearance characteristics and completed measures of anti-fat attitudes, thin ideal internalization, and demographics. Participants rated thin and overweight models equally attractive and sexy. Viewing overweight models showed a significant reduction in anti-fat attitudes. There were no effects for thin models or evaluation ratings. Discussion focuses on the implications of positive images of overweight individuals on social attitudes.     

Corrected maximum likelihood estimators in heteroscedastic symmetric nonlinear models

In this article, we derive general matrix formulae for second-order biases of maximum likelihood estimators (MLEs) in a class of heteroscedastic symmetric nonlinear regression models, thus generalizing some results in the literature. This class of regression models includes all symmetric continuous distributions, and has a wide range of practical applications in various fields such as engineering, biology, medicine and economics, among others. The variety of distributions with different kurtosis coefficients than the normal may give more flexibility in the choice of an appropriate distribution, particularly to accommodate outlying and influential observations. We derive a joint iterative process for estimating the mean and dispersion parameters. We also present simulation studies for the biases of the MLEs.     

Inter-group contact and out-group altruism after violence

Altruism among humans is common. It is especially prominent among in-group members. However, we are struck by results from laboratory-in-the-field experiments with out-group members of different ethnic or religious backgrounds. In all instances, the groups were rivals in civil wars. While we find almost no altruistic behavior among groups that were engaged in fighting, out-group altruism emerges with the passage of time. To address the underlying mechanism that might explain this puzzling result, we use a laboratory experiment that sorts between a norms revision explanation and a contact hypothesis explanation. Our findings show that contact with out-group members, in a mutually beneficial task, results in a reversion to prior levels of out-group altruism following conflict. Our findings reinforce the idea that deeply held attitudes toward a stigmatized out-group change following productive interactions with those out-group members. It is clear that hostility between groups need not persist over time.     

The boomerang effect of psychological interventions

Research has found that teaching people about psychological biases can help counteract biased behavior. On the other hand, due to the innate need for preservation of a positive self-image, it is likely that teaching people about biases they hold, may cause a boomerang effect in cases where being associated with a specific bias implies negative social connotations. In the three studies below we examine situations in which psychological bias implies negatively associated behavior, and show that teaching people about bias in those contexts can be counterproductive.     

Non uniform exponential bounds on normal approximation by Stein’s method and monotone size bias couplings

It is known that the normal approximation is applicable for sums of non negative random variables, W, with the commonly employed couplings. In this work, we use the Stein’s method to obtain a general theorem of non uniform exponential bound on normal approximation base on monotone size bias couplings of W. Applications of the main result to give the bound on normal approximation for binomial random variable, the number of bulbs on at the terminal time in the lightbulb process, and the number of m runs are also provided.     

Gender,status, and psychiatric labels

We examine a key modified labeling theory proposition—that a psychiatric label increases vulnerability to competence-based criticism and rejection—within task- and collectively oriented dyads comprised of same-sex individuals with equivalent education. Drawing on empirical work that approximates these conditions, we expect the proposition to hold only among men. We also expect education, operationalized with college class standing, to moderate the effects of gender by reducing men’s and increasing women’s criticism and rejection. But, we also expect the effect of education to weaken when men work with a psychiatric patient. As predicted, men reject suggestions from teammates with a psychiatric history more frequently than they reject suggestions from other teammates, while women’s resistance to influence is unaffected by their teammate’s psychiatric status. Men also rate psychiatric patient teammates as less powerful but no lower in status than other teammates, while women’s teammate assessments are unaffected by their teammate’s psychiatric status. Also as predicted, education reduces men’s resistance to influence when their teammate has no psychiatric history. Education also increases men’s ratings of their teammate’s power, as predicted, but has no effect on women’s resistance to influence or teammate ratings. We discuss the implications of these findings for the modified labeling theory of mental illness and status characteristics theory.     

Hypothesis Tests for Neyman's Bias in Case–Control Studies

Survival bias is a long recognized problem in case–control studies, and many varieties of bias can come under this umbrella term. We focus on one of them, termed Neyman's bias or ‘prevalence–incidence bias’. It occurs in case–control studies when exposure affects both disease and disease-induced mortality, and we give a formula for the observed, biased odds ratio under such conditions. We compare our result with previous investigations into this phenomenon and consider models under which this bias may or may not be important. Finally, we propose three hypothesis tests to identify when Neyman's bias may be present in case–control studies. We apply these tests to three data sets, one of stroke mortality, another of brain tumors, and the last of atrial fibrillation, and find some evidence of Neyman's bias in the former two cases, but not the last case.     

Early socialization of hostile attribution bias: The roles of parental attributions,parental discipline,and child attributes

The goal of this study was to examine child and parent predictors of children's hostile attribution bias (HAB) with a particular focus on exploring the associations between parents’ early attribution of child misbehavior and children's HAB in the transition to school age. Participants were 241 children (118 girls) of middle‐income families who were at risk for school‐age conduct problems. Multi‐method, multi‐informant data were collected on maternal attributions of child misbehavior, parental use of corporal punishment, and child attributes (i.e., verbal IQ, effortful control, theory of mind, and emotional understanding) at 3 years, and child HAB in ambiguous situations at 6 years. Results indicated that mothers’ internal explanations for children's misconduct may either reduce or increase children's later HAB depending on the specific content of attributions, such that mothers’ belief that children misbehave because of their internal state (i.e., emotional state or temperament) was associated with lower levels of child HAB, whereas attributing power‐based motives (i.e., manipulative, controlling intentions) in children was associated with higher levels of HAB. The findings are discussed with respect to appreciating the complexity of parents’ explanations for children's behavior, and considering parental cognition as a potential target for early identification and prevention of child HAB and related problems.