Change-Point Tests for the Error Distribution in Non-parametric Regression

Abstract.  Several testing procedures are proposed that can detect change-points in the error distribution of non-parametric regression models. Different settings are considered where the change-point either occurs at some time point or at some value of the covariate. Fixed as well as random covariates are considered. Weak convergence of the suggested difference of sequential empirical processes based on non-parametrically estimated residuals to a Gaussian process is proved under the null hypothesis of no change-point. In the case of testing for a change in the error distribution that occurs with increasing time in a model with random covariates the test statistic is asymptotically distribution free and the asymptotic quantiles can be used for the test. This special test statistic can also detect a change in the regression function. In all other cases the asymptotic distribution depends on unknown features of the data-generating process and a bootstrap procedure is proposed in these cases. The small sample performances of the proposed tests are investigated by means of a simulation study and the tests are applied to a data example.     

Through the Ages: Developing Relationships Between the Young and the Old

This article evaluates a program between students at a primary school and aged care residents. The aim of the program was to increase respect and appreciation between the groups. Visiting programs between children and the elderly are well documented, and assumes that the contact will benefit both groups. However the research is contradictory. To ensure that this program was achieving its goals, pre-post test data using the Children’s Perceptions of Aging and Elderly test was collected. Significant improvements in attitude were seen in two items. Overall, there was an improvement in attitude in 12 of the 18 instrument items.     

Mental Health and Clinical Correlates in Lesbian,Gay, Bisexual,and Queer Young Adults

Abstract

Objective: This study examined the prevalence of mental health disorders and their clinical correlates in a university sample of lesbian, gay, bisexual, and queer (LGBQ) students. Participants: College students at a large public university. Methods: An anonymous, voluntary survey was distributed via random e-mail generation to university students during April and May of 2011. LGBQ students were compared with their heterosexual counterparts on psychological and physical status as well as academic performance. Results: LGBQ students reported worse depressive symptoms, higher levels of perceived stress, considered themselves less attractive, and were more likely to be overweight. LGBQ students were significantly more likely to report histories of affective, substance use, and certain anxiety disorders as well as compulsive sexual behavior and compulsive buying. Conclusions: The higher rates of many psychiatric conditions among LGBQ students underscore the need for universities to provide LGBQ students a nonjudgmental environment to discuss sexual orientation and health issues.     

Drinking Game Participation Among Undergraduate Students Attending National Alcohol Screening Day

Abstract

Objectives, Participants, Methods: Drinking game participation has increased in popularity among college students and is associated with increased alcohol consumption and alcohol-related problems. The current study investigated drinking game participation among 133 undergraduates attending National Alcohol Screening Day (NASD) in April of 2007. Results: A large percentage of the sample reported lifetime (77%) and recent (52%) drinking game participation. Males were more likely to report recent participation and reported higher levels of consumption while playing drinking games. Drinking game participants were more likely to experience a range of alcohol-related problems, and the relationship between drinking game participation and alcohol-related problems was mediated by weekly alcohol consumption. Conclusions: These results suggest that drinking game participation is a risk factor for elevated levels of alcohol consumption and alcohol-related problems. Programs should be developed to educate students about the risks of drinking game participation, and prevention programs like NASD should address drinking games.     

Comparison of Separable Components in Different Samples

Abstract.  Imagine we have two different samples and are interested in doing semi- or non-parametric regression analysis in each of them, possibly on the same model. In this paper, we consider the problem of testing whether a specific covariate has different impacts on the regression curve in these two samples. We compare the regression curves of different samples but are interested in specific differences instead of testing for equality of the whole regression function. Our procedure does allow for random designs, different sample sizes, different variance functions, different sets of regressors with different impact functions, etc. As we use the marginal integration approach, this method can be applied to any strong, weak or latent separable model as well as to additive interaction models to compare the lower dimensional separable components between the different samples. Thus, in the case of having separable models, our procedure includes the possibility of comparing the whole regression curves, thereby avoiding the curse of dimensionality. It is shown that bootstrap fails in theory and practice. Therefore, we propose a subsampling procedure with automatic choice of subsample size. We present a complete asymptotic theory and an extensive simulation study.     

Testing Monotonicity of Regression Functions – An Empirical Process Approach

We propose several new tests for monotonicity of regression functions based on different empirical processes of residuals and pseudo‐residuals. The residuals are obtained from an unconstrained kernel regression estimator whereas the pseudo‐residuals are obtained from an increasing regression estimator. Here, in particular, we consider a recently developed simple kernel‐based estimator for increasing regression functions based on increasing rearrangements of unconstrained non‐parametric estimators. The test statistics are estimated distance measures between the regression function and its increasing rearrangement. We discuss the asymptotic distributions, consistency and small sample performances of the tests.     

Estimating the Conditional Error Distribution in Non‐parametric Regression

Abstract. We consider a general non‐parametric regression model, where the distribution of the error, given the covariate, is modelled by a conditional distribution function. For the estimation, a kernel approach as well as the (kernel based) empirical likelihood method are discussed. The latter method allows for incorporation of additional information on the error distribution into the estimation. We show weak convergence of the corresponding empirical processes to Gaussian processes and compare both approaches in asymptotic theory and by means of a simulation study.     

Medication Abortion Within a Student Health Care Clinic: A Review of the First 46 Consecutive Cases

Abstract

Objective: Medication abortion with mifepristone and misoprostol has been available in the United States since 2000. The authors reviewed the first 46 medication abortion cases conducted at a university-based student health care clinic to determine the safety and feasibility of medication abortion in this type of clinical setting. Participants: Female patients presenting for medication abortion at a student health care clinic between October 1, 2006, and April 1, 2009. Methods: Retrospective consecutive case review. Results: Successful completion not requiring uterine aspiration occurred in 85% of the cases that were not lost to follow-up. Six cases (15%) required uterine aspiration for completion: 3 underwent uterine aspiration only; 3 had aspiration after failing an additional dose of misoprostol. Only 1 patient visited the emergency room. There were no hospitalizations. Conclusions: Medication abortion services in a student health care clinic are safe and feasible. However, additional treatment may be required with some patients.     

Trial and Lifetime Smoking Risks Among African American College Students

Abstract

The authors surveyed 614 African American university students to determine the magnitude of cigarette use, identify risk factors, and develop models to predict smoking. More than half (58.3%) of the participants had smoked at least once, and 9.3% of that group were lifetime smokers. Among the lifetime smokers, 71.3% had smoked during the 30 days preceding the survey. More women (66.8%) than men (56.1%) had tried smoking and were classed as lifetime smokers. Residence, parental, and peer smoking (current and childhood) were associated with trying smoking; age, race/ethnicity, and marital status were additional factors for becoming a lifetime smoker. The risk of being a lifetime smoker was reduced when neither friends nor parents of the student smoked and the student viewed spirituality as important. The results of this study add to the growing understanding of health risk behaviors among African Americans and can be useful in reducing smoking.