New tests for stochastic order with application to case control studies

It is shown that if a binary regression function is increasing then retrospective sampling induces a stochastic ordering of the covariate distributions among the responders, which we call cases, and the non-responders, which we call controls. We also show that if the covariate distributions are stochastically ordered then the regression function must be increasing. This means that testing whether the regression function is monotone is equivalent to testing whether the covariate distributions are stochastically ordered. Capitalizing on these new probabilistic observations we proceed to develop two new non-parametric tests for stochastic order. The new tests are based on either the maximally selected, or integrated, chi-bar statistic of order one. The tests are easy to compute and interpret and their large sampling distributions are easily found. Numerical comparisons show that they compare favorably with existing methods in both small and large samples. We emphasize that the new tests are applicable to any testing problem involving two stochastically ordered distributions.     

The Influence of Biostatistics at the National Heart,Lung, and Blood Institute

Since the early 1950s, the National Heart, Lung, and Blood Institute (NHBLI) has conducted a long series of influential randomized clinical trials in heart, lung, and blood diseases. The biostatisticians at the Institute have been central to the design, conduct, monitoring, and final analyses of these trials. The uniquely favorable deck of cards the group of biostatisticians at the Institute has been dealt over the six and half decades of the group's life has led to contributions that have had a major impact on the fields of biostatistics and clinical trials. The leaders of the NHLBI and its several Divisions have valued the independence, creativity, and collaborative interactions of statisticians within the Institute. The medical problems the Institute faced impelled the statisticians to develop methodology that would address questions of great public importance. Perhaps most importantly, the individual members of the group had a collective vision passed from member to member over time that new methodology must fit the questions being asked. The group has always had the technical ability to develop new methods and the conviction that they were responsible for ensuring that they could explain their methods to the clinicians with whom they worked.     

Assessment of Inhalation Exposures and Potential Health Risks to the General Population that Resulted from the Collapse of the World Trade Center Towers

In the days following the collapse of the World Trade Center (WTC) towers on September 11, 2001 (9/11), the U.S. Environmental Protection Agency (EPA) initiated numerous air monitoring activities to better understand the ongoing impact of emissions from that disaster. Using these data, EPA conducted an inhalation exposure and human health risk assessment to the general population. This assessment does not address exposures and potential impacts that could have occurred to rescue workers, firefighters, and other site workers, nor does it address exposures that could have occurred in the indoor environment. Contaminants evaluated include particulate matter (PM), metals, polychlorinated biphenyls, dioxins, asbestos, volatile organic compounds, particle-bound polycyclic aromatic hydrocarbons, silica, and synthetic vitreous fibers (SVFs). This evaluation yielded three principal findings. (1) Persons exposed to extremely high levels of ambient PM and its components, SVFs, and other contaminants during the collapse of the WTC towers, and for several hours afterward, were likely to be at risk for acute and potentially chronic respiratory effects. (2) Available data suggest that contaminant concentrations within and near ground zero (GZ) remained significantly elevated above background levels for a few days after 9/11. Because only limited data on these critical few days were available, exposures and potential health impacts could not be evaluated with certainty for this time period. (3) Except for inhalation exposures that may have occurred on 9/11 and a few days afterward, the ambient air concentration data suggest that persons in the general population were unlikely to suffer short-term or long-term adverse health effects caused by inhalation exposures. While this analysis by EPA evaluated the potential for health impacts based on measured air concentrations, epidemiological studies conducted by organizations other than EPA have attempted to identify actual impacts. Such studies have identified respiratory effects in worker and general populations, and developmental effects in newborns whose mothers were near GZ on 9/11 or shortly thereafter. While researchers are not able to identify specific times and even exactly which contaminants are the cause of these effects, they have nonetheless concluded that exposure to WTC contaminants (and/or maternal stress, in the case of developmental effects) resulted in these effects, and have identified the time period including 9/11 itself and the days and few weeks afterward as a period of most concern based on high concentrations of key pollutants in the air and dust.     

Children's Cognitive Perceptions of 6/49 Lottery Tickets

Recent studies have shown the high prevalence of youth gambling behavior. In particular, lottery ticket purchases among children and adolescents appear to be a highly preferred activity. Despite this fact, most research has focused on the underlying erroneous cognitions used by adults when selecting lottery tickets. This study examines the cognitive perceptions of children while engaged in selecting 6/49 lottery tickets. One hundred sixty-seven children (61 females; 106 males) from grades 3, 5, and 7 were asked to rank pre-selected 6/49 lottery tickets which were classified into a) long series, b) specific patterns, c) non equilibrated numbers, or d) perceived random selections. Children verbalized their rationale for selecting each ticket and were permitted to change the numbers on the lottery tickets they liked least in order to make them to more likely to be the winning ticket. Findings, in general, revealed small developmental differences in the types of underlying cognitive heuristics used by the children. The use of cognitive heuristics underlying the concept of randomness and the use of significant and meaningful numbers was observed to increase as children got older. Children between 9 and 11 were found to have employed the cluster heuristic more frequently than older children, ages 12–13. The results are interpreted in terms of the cognitive developmental changes in children's perceptions and the potential implication for gambling prevention programs are provided.     

Motivational or dispositional? The type of inference shapes the effectiveness of leader anger expressions

Existing leadership research has presented conflicting views on the effects of leader anger expressions. The present research aims to reconcile these findings by proposing that the type of inferences followers make (i.e., motivation-focused inference or trait-focused inference) is a key factor determining the outcomes of leader anger expressions. Through one survey study (Study 1) and two experimental studies (Studies 2 and 3), the present research indicates that the effectiveness of leader anger expressions is associated with the type of inferences followers draw from the anger. In general, we found support for the negative relationship between trait-focused inferences and leader effectiveness, but were unable to properly test the positive relationship between motivation-focused inferences and leader effectiveness due to the lack of appropriate instrumental variables. We also investigated whether followers' implicit theories of personality (i.e., entity versus incremental theory) would moderate the effect of leader anger expressions on the type of inferences made by followers, which in turn shapes leader effectiveness. The results of Study 3 provide evidence of the moderating role of implicit theories of personality. Theoretical contributions and practical implications of the present research are discussed.     

What do young children know about sex? Research on the sexual knowledge of children between the ages of 2 and 6 years

We investigated the sexual knowledge of 63 Dutch children in the age range 2–6 years. Boys and girls were equally represented in the sample. The children had an average, or above‐average IQ and none of them had any experience of sexual abuse. It was found that young children have a very limited knowledge of sexuality. They only possess some basic knowledge of genital differences, gender identity, sexual body parts and (non‐sexual) functions of the genitals. Knowledge of pregnancy and birth, reproduction and adult sexual behaviour was found to be very limited and decreased in the order presented here. Non‐sexually abused children appear to interpret situations that show physical intimacy between adults and children in terms of their own experiences. None of the children talked about sexual activities. Older children generally knew more than younger ones. No significant differences in knowledge between boys and girls were found. Copyright © 2000 John Wiley & Sons, Ltd.