Bootstrap tests for the error distribution in linear and nonparametric regression models

In this paper we investigate several tests for the hypothesis of a parametric form of the error distribution in the common linear and nonparametric regression model, which are based on empirical processes of residuals. It is well known that tests in this context are not asymptotically distribution-free and the parametric bootstrap is applied to deal with this problem. The performance of the resulting bootstrap test is investigated from an asymptotic point of view and by means of a simulation study. The results demonstrate that even for moderate sample sizes the parametric bootstrap provides a reliable and easy accessible solution to the problem of goodness-of-fit testing of assumptions regarding the error distribution in linear and nonparametric regression models. --goodness-of-fit,residual process,parametric bootstrap,linear model,analysis of variance,M-estimation,nonparametric regression

A note on testing symmetry of the error distribution in linear regression models

In the classical linear regression model the problem of testing for symmetry of the error distribution is considered. The test statistic is a functional of the difference between the two empirical distribution functions of the estimated residuals and their counterparts with opposite signs. The weak convergence of the difference process to a Gaussian process is established. The covariance structure of this process depends heavily on the density of the error distribution, and for this reason the performance of a symmetric wild bootstrap procedure is discussed in asymptotic theory and by means of a simulation study. --M-estimation,goodness-of-fit tests,testing for symmetry,empirical process of residuals,linear model

Empirical likelihood estimators for the error distribution in nonparametric regression models

The aim of this paper is to show that existing estimators for the error distribution in nonparametric regression models can be improved when additional information about the distribution is included by the empirical likelihood method. The weak convergence of the resulting new estimator to a Gaussian process is shown and the performance is investigated by comparison of asymptotic mean squared errors and by means of a simulation study. As a by-product of our proofs we obtain stochastic expansions for smooth linear estimators based on residuals from the nonparametric regression model. --empirical distribution function,empirical likelihood,error distribution,estimating function,nonparametric regression,Owen estimator

Tests in a Case-Control Design Including Relatives

We present a new approach to handle dependencies within the general framework of case-control designs, illustrating our approach by a particular application from the field of genetic epidemiology. The method is derived for parent-offspring trios, which will later be relaxed to more general family structures. For applications in genetic epidemiology we consider tests on equality of allele frequencies among cases and controls utilizing well-known risk measures to test for independence of phenotype and genotype at the observed locus. These test statistics are derived as functions of the entries in the associated contingency table containing the numbers of the alleles under consideration in the case and the control group. We find the joint asymptotic distribution of these entries, which enables us to derive critical values for any test constructed on this basis. A simulation study reveals the finite sample behavior of our test statistics. --association tests,contingency tables,dependent data,risk measures

Dependence of TIMP-1 plasma levels on preanalytical specimen handling

Background: Tissue inhibitor of metalloproteinases-1 (TIMP-1) in blood might be a helpful biomarker in various diseases. However, various authors report that TIMP-1 is dependent on preanalytical procedures. Our study was performed to determine how storage conditions and time to centrifugation influence TIMP-1. Materials and Methods: Twenty-six blood specimens were collected from each of 20 volunteers. Two specimens from each person were centrifuged/measured within 1 h after venipuncture and frozen at -80 degrees C. They were thawed once or twice within 72 h. Eight specimens were stored at 20 degrees C in daylight, 8 at 20 degrees C covered and 8 at 4 C in daylight. Four of each of these 8 specimens were mixed once a day until centrifugation. A mixed and an unmixed specimen of each group was centrifuged/measured after 3, 6, 24 and 72 h. Results: TIMP-1 increased after freeze/ thaw (p < 0.001). Mixing blood specimens more than once caused increased TIMP-1 (p < 0.001). TIMP-1 increased within 3 h of storage (p < 0.001). The increase was lower in specimens covered and refrigerated (p < 0.001). Conclusion: TIMP-1 is unstable and has to be evaluated carefully. Blood should be centrifuged directly after venipuncture. For routine application, specimen handling must be standardized and carefully followed. Research should be done on specimens handled identically. Copyright (C) 2008 S. Karger AG, Basel

Bootstrap Tests for the Error Distribution in Linear and Nonparametric Regression Models

In this paper we investigate several tests for the hypothesis of a parametric form of the error distribution in the common linear and nonparametric regression model, which are based on empirical processes of residuals. It is well known that tests in this context are not asymptotically distribution-free and the parametric bootstrap is applied to deal with this problem. The performance of the resulting bootstrap test is investigated from an asymptotic point of view and by means of a simulation study. The results demonstrate that even for moderate sample sizes the parametric bootstrap provides a reliable and easy accessible solution to the problem of goodness-of-fit testing of assumptions regarding the error distribution in linear and nonparametric regression models

A Note on Testing Symmetry of the Error Distribution in Linear Regression Models

In the classical linear regression model the problem of testing for symmetry of the error distribution is considered. The test statistic is a functional of the difference between the two empirical distribution functions of the estimated residuals and their counterparts with opposite signs. The weak convergence of the difference process to a Gaussian process is established. The covariance structure of this process depends heavily on the density of the error distribution, and for this reason the performance of a symmetric wild bootstrap procedure is discussed in asymptotic theory and by means of a simulation study

Spatio-temporal use of the urban habitat by feral pigeons (Columba livia )

Feral pigeons are descendants of wild rock pigeons that have adapted to the urban habitat. They have partially conserved the foraging behaviour of their wild ancestors (flights to agricultural areas) but have also developed new habits. Previous studies on the foraging strategies of feral pigeons have given various results, e.g. maximum distances reached by the pigeons (measured in a straight line from the resting places) differed between 0.3-0.5km and 18-25km. This study focuses on the spatio-temporal activity of feral pigeons in the urban habitat. We equipped 80 free-living feral pigeons from Basel, Switzerland with GPS receivers. We found three different foraging strategies for pigeons in Basel: (1) in the streets, squares and parks near the home loft, (2) in agricultural areas surrounding the city, (3) on docks and railway lines in harbours. The maximum distance reached by a pigeon was 5.29km. More than 32% of the pigeons remained within 0.3km of the home lofts and only 7.5% flew distances of more than 2km. Females covered significantly longer distances than males, preferring to fly to more abundant and predictable food sources. Temporal activity patterns showed to be influenced by sex, breeding state and season. In contrast to wild rock pigeons and to feral pigeons in other cities, pigeons in Basel showed a clear bimodal activity pattern for breeding birds only. The differences between our results and those of other studies seem to be partly method-dependent, as the GPS-technique allows to record the pigeons' localisations continuously in contrast to other methods. Other differences might be due to different kinds of food supply in the various cities. Our study shows that feral pigeons have individual foraging strategies and are flexible enough to adapt to different urban environment

Meaning Making and Positive Development with Adolescent Girls: Using the Arts, Community, Reflections, and Service

This study explores the essential factors needed in adolescent youth programs, which intend to promote resilience, well being, and meaning making as a part of the healthy development of adolescent girls. The research explores the role of the arts, community building, mentoring, service, and reflection on this development. The context is Side by Side, a summer leadership development program. In a qualitative case study approach, the data is organized primarily from the written and spoken words of seven young women who participated in the program

“More Gruesome a Chick Looks, the More I Respect Her Skills”: Toxic Masculinity, Emphasized Femininity, and Media Portrayal/Fan Consumption of the Emergence of Women’s Mixed Martial Arts through Shayna Baszler, Invicta FC, and Ronda Rousey, 2003-2013

This paper exams how online media and fans reacted to the presence of two female professional mixed martial arts (MMA) fighters, Shayna Baszler and Ronda Rousey, and the emergence of an all-women\u27s MMA promotion, Invicta FC, in the years between 2003 and 2013. By analyzing articles from major MMA news sites, along with attached fan commentary, this dissertation strives to answer whether traditional concepts of feminine behavior influenced media coverage and associated fan reactions regarding women in MMA and how often these remarks shifted into toxicity. One important finding was that the fans’ “male gaze” was omnipresent from the beginning to the end of the study period. Another significant discovery found that the online fans\u27 reaction to Baszler and Invicta FC contrasted to their dialogue around Rousey. The latter was more harshly criticized (and fans less open to positive sentiments) because she threatened the all-masculine preserve of the Ultimate Fighting Championship, i.e., the major leagues of MMA. There were four primary conclusions. First, over the 10-year study period fans became more willing to acknowledge female technical skill, but many toxic dissenters remained. Second, discussions of female fragility were few and far between. Third, the use of humor was common in transforming benign masculine statements into toxic ones. Most importantly, a sizable portion of the online fanbase felt that women competing in MMA defied traditional feminine roles and that resulted in a toxic masculine reaction