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101.
This paper presents a procedure for testing the hypothesis that the underlying distribution of the data is elliptical when using robust location and scatter estimators instead of the sample mean and covariance matrix. Under mild assumptions that include elliptical distributions without first moments, we derive the test statistic asymptotic behavior under the null hypothesis and under special alternatives. Numerical experiments allow to compare the behavior of the tests based on the sample mean and covariance matrix with that based on robust estimators, under various elliptical distributions and different alternatives. We also provide a numerical comparison with other competing tests. 相似文献
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103.
Transition to parenthood in Switzerland takes place in a particularly gendered institutional context. It is the only European country where men do not have access to any kind of statutory parental or paternity leaves. This study empirically investigates the extent to which institutional change – through paternity leave implementation at the company level – challenges gendered representations and practices of fatherhood. The study draws on a mixed methods case study conducted in a public administration which implemented a one-month paid paternity leave. Using register data about leave recipients (N = 95), we adopt a longitudinal and typological approach of leave uptake patterns by means of sequence and cluster analyses. In-depth interviews conducted with recipient fathers and managers working for the company (n = 30) enable an analysis of the implementation process and the meanings associated with paternity leave and fatherhood. Results show that paternity leave implementation challenged, in a limited way, gendered representations and practices of fatherhood. Fatherhood was made more visible within the company, but workplace characteristics and informal norms influenced fathers' leave uptake. Overall, motherhood and fatherhood were associated with different and specialized responsibilities. Fathers mainly had a secondary and temporary role with the newborn, while mothers were the central and taken-for-granted parent. 相似文献
104.
This article analyses the relevance of the agency problems that exist between shareholders and managers (type I agency problems) and between majority and minority shareholders (type II agency problems), in determining the composition of the board of directors, differentiating between family owned and non-family owned firms. The hypotheses are tested on a sample of 173 Spanish listed companies for the period 2004–2011. The results of our study indicate that, on one hand, as type I agency problems increase, firms increase their percentage of outside directors and, on the other, as type II agency problems increase, firms increase the ratio of independent to nominee directors. Whether the company is a family firm or not does moderate the influence of insider ownership over the composition of the board. Generally speaking, our findings support the view that firms configure their board of directors in such a way as to best signal to the market both efficient management and a balance of the interests of all shareholders. Likewise, these results could be taken into account when formulating recommendations on the composition of the board of directors. 相似文献
105.
Maturation of tactile sensitivity prior to term was examined in 36 preterm and 13 full‐term infants using a fixed‐trial, habituation procedure. Each infant was presented with a series of 8 habituation (arm stroke), 2 novel (arm lift), and 2 recovery (arm stroke) stimulus trials while heart rate and body movements were recorded. Maturation was observed with a gradual increase in the magnitude of the stimulus‐elicited cardiac acceleration and cardiac‐movement coupling from 30 to 40 weeks postconceptional age. The majority of infants displayed habituation—an excitatory response (heart rate acceleration and body movement)—to the initial presentation of a tactile stimulus, response decline with repeated stimulations, and renewed response to a novel stimulus. A substantial number of infants (40%) failed to respond initially to the tactile stimulus, increased responding over several stimulus presentations, and failed to discriminate the presentation of a novel stimulus. We speculate that these differences in response patterns observed over all ages represent individual difference in the perception of stimulus intensity. 相似文献
106.
Consistent Smooth Bootstrap Kernel Intensity Estimation for Inhomogeneous Spatial Poisson Point Processes
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Isabel Fuentes‐Santos Wenceslao González‐Manteiga Jorge Mateu 《Scandinavian Journal of Statistics》2016,43(2):416-435
Non‐parametric estimation and bootstrap techniques play an important role in many areas of Statistics. In the point process context, kernel intensity estimation has been limited to exploratory analysis because of its inconsistency, and some consistent alternatives have been proposed. Furthermore, most authors have considered kernel intensity estimators with scalar bandwidths, which can be very restrictive. This work focuses on a consistent kernel intensity estimator with unconstrained bandwidth matrix. We propose a smooth bootstrap for inhomogeneous spatial point processes. The consistency of the bootstrap mean integrated squared error (MISE) as an estimator of the MISE of the consistent kernel intensity estimator proves the validity of the resampling procedure. Finally, we propose a plug‐in bandwidth selection procedure based on the bootstrap MISE and compare its performance with several methods currently used through both as a simulation study and an application to the spatial pattern of wildfires registered in Galicia (Spain) during 2006. 相似文献
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108.
Thomas J. Silber M.D. M.A.S.S. Mary Capon M.D. Dr. Isabel Kuperschmit M.D. 《Journal of American college health : J of ACH》2013,61(6):229-233
Abstract “Blood Glucose Control and the Evolution of Diabetic Retinopathy and Albuminuria: A Preliminary Multicenter Trial,” The Kroc Collaborative Study Group. We conducted a prospective multicenter randomized trial to determine both the feasibility of maintaining blood glucose control at differing levels and the effect of improved control on diabetic microangiopathy and albuminuria. Seventy patients with diabetes (low C-peptide level) with nonproliferative retinopathy were randomly assigned to continuous subcutaneous insulin infusion or unchanged conventional injection treatment. At entry, both groups had similar demographic, clinical, and glycemic characteristics. Over the succeeding eight months, mean 24-hour glucose concentrations (175 ± 9 mg per deciliter) and glycosylated hemoglobin levels (10.0 ± 0.3%) remained elevated during conventional treatment but fell to nearly normal levels (117 ± 6 mg per deciliter and 8.1 ± 0.2%, respectively) with continuous insulin infusion. The frequency of biochemical hypoglycemia (< 40 mg of blood glucose per deciliter) was similar in both groups, but ketoacidosis occurred only during continuous infusion. The level of retinopathy, assessed from photographs, progressed in both groups. Continuous infusion was associated with slightly more deterioration, mainly because of the appearance of soft exudates and intraretinal microvascular abnormalities. In contrast, elevated albumin-excretion rates fell during continuous infusion but not during conventional treatment. We conclude that maintenance of differing levels of blood glucose is feasible in a multicenter trial and that a nearly normal blood glucose level for eight months does not retard progression of, and may initially worsen, established retinopathy. These preliminary observations indicate the need for longer trials (particularly of primary prevention). (New England Journal of Medicine 1984;311:365-72.) 相似文献
109.
The authors propose to estimate nonlinear small area population parameters by using the empirical Bayes (best) method, based on a nested error model. They focus on poverty indicators as particular nonlinear parameters of interest, but the proposed methodology is applicable to general nonlinear parameters. They use a parametric bootstrap method to estimate the mean squared error of the empirical best estimators. They also study small sample properties of these estimators by model‐based and design‐based simulation studies. Results show large reductions in mean squared error relative to direct area‐specific estimators and other estimators obtained by “simulated” censuses. The authors also apply the proposed method to estimate poverty incidences and poverty gaps in Spanish provinces by gender with mean squared errors estimated by the mentioned parametric bootstrap method. For the Spanish data, results show a significant reduction in coefficient of variation of the proposed empirical best estimators over direct estimators for practically all domains. The Canadian Journal of Statistics 38: 369–385; 2010 © 2010 Statistical Society of Canada 相似文献
110.
Derek T. Dangerfield II Nina T. Harawa M. Isabel Fernandez Sybil Hosek Jennifer Lauby Heather Joseph 《Journal of sex research》2013,50(8):1012-1021
Little attention has focused on generational or age-related differences in human immunodeficiency virus/sexually transmitted infection (HIV/STI) risk behaviors among Black men who have sex with men and women (BMSMW). We examined sexual risk behaviors between BMSMW ages 40 and under compared to over age 40. Analysis was conducted using Centers for Disease Control and Prevention (CDC)–sponsored intervention data among BMSMW in Los Angeles, Chicago, and Philadelphia (n = 546). Pearson’s chi-square tests were conducted to evaluate associations between age groups and behavioral outcomes. Logistic regression was used to evaluate the odds of behavioral outcomes by age group, adjusting for sexual orientation and study location, within strata of HIV status. HIV-positive BMSMW over age 40 had 62% reduced odds of having a nonmain female partner of HIV-negative or unknown status compared to those ages 40 and under (adjusted odds ratio [AOR] 0.38, 95% confidence interval [CI] = 0.15, 0.95). Among HIV-negative BMSMW, the older cohort was associated with greater odds of having condomless insertive anal intercourse (IAI) with most recent main male partner (AOR 2.44, 95% CI = 1.12, 5.32) and having a concurrent partnership while with their recent main female partner (AOR = 2.6, 95% CI = 1.10, 4.67). For both groups, odds of engaging in certain risk behaviors increased with increasing age. Prevention efforts should consider generational differences and age in HIV risks among BMSMW. 相似文献