排序方式: 共有95条查询结果,搜索用时 31 毫秒
51.
Feng-Shou Ko 《统计学通讯:理论与方法》2013,42(15):2681-2698
A proposed method based on frailty models is used to identify longitudinal biomarkers or surrogates for a multivariate survival. This method is an extention of earlier models by Wulfsohn and Tsiatis (1997) and Song et al. (2002). In this article, similar to Henderson et al. (2002), a joint likelihood function combines the likelihood functions of the longitudinal biomarkers and the multivariate survival times. We use simulations to explore how the number of individuals, the number of time points per individual and the functional form of the random effects from the longitudianl biomarkers influence the power to detect the association of a longitudinal biomarker and the multivariate survival time. The proposed method is illustrate by using the gastric cancer data. 相似文献
52.
Feng-Shou Ko 《统计学通讯:理论与方法》2014,43(24):5241-5248
In the conventional concept, the variance of a tolerance interval from the measurements is a single component, and the sample size for quality control process was estimated by the variance of a single component. However, we can find examples in recent about several components that could vary in their measurements, so an approximate method must be found to modify the conventional tolerance interval. In our paper, we develop an approach to calculate the sample size for a two-sided tolerance interval including several components in the variance from the measurements. An example is presented to illustrate our proposed method. 相似文献
53.
Feng-Shou Ko 《统计学通讯:理论与方法》2014,43(16):3329-3342
In recent years, joint analysis of longitudinal measurements and survival data has received much attention. However, previous work has primarily focused on a single failure type for the event time. In this article, we consider joint modeling of repeated measurements and competing risks failure time data to allow for more than one distinct failure type in the survival endpoint so we fit a cause-specific hazards sub-model to allow for competing risks, with a separate latent association between longitudinal measurements and each cause of failure. Besides, previous work does not focus on the hypothesis to test a separate latent association between longitudinal measurements and each cause of failure. In this article, we derive a score test to identify longitudinal biomarkers or surrogates for a time to event outcome in competing risks data. With a carefully chosen definition of complete data, the maximum likelihood estimation of the cause-specific hazard functions is performed via an EM algorithm. We extend this work and allow random effects to be present in both the longitudinal biomarker and underlying survival function. The random effects in the biomarker are introduced via an explicit term while the random effect in the underlying survival function is introduced by the inclusion of frailty into the model.
We use simulations to explore how the number of individuals, the number of time points per individual and the functional form of the random effects from the longitudinal biomarkers considering heterogeneous baseline hazards in individuals influence the power to detect the association of a longitudinal biomarker and the survival time. 相似文献
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55.
This study examined prevalence and correlates of suicidal ideation and dating partner violence in a cohort of 651 university students in social sciences classes at three universities in Hong Kong. A standard questionnaire was completed within one class period to examine the rates of occurrence of physical assault perpetration and suicidal ideation. Separate rates are presented for male and female perpetrators and for severe and overall levels of violence. The differences between subjects having suicidal ideation are compared using t tests. Logistic regression is used to predict the presence or absence of physical assault in the preceding year of reporting and suicidal ideation based on the variables such as Personal Relationship Profile, age, relationship length, and socioeconomic status. Results showed that 55% of suicidal persons had a history of violence, whereas 39% of violent people had a history of suicidal ideation. Logistic regression showed that physical assault shared a total of seven associated factors with suicidal ideation. Suicidal ideation seems to have no direct relation to physical and sexual assault, but they do share some common associated factors that are essential for the development of suicide prevention. 相似文献
56.
In this paper, we extend the focused information criterion (FIC) to copula models. Copulas are often used for applications where the joint tail behavior of the variables is of particular interest, and selecting a copula that captures this well is then essential. Traditional model selection methods such as the Akaike information criterion (AIC) and the Bayesian information criterion (BIC) aim at finding the overall best‐fitting model, which is not necessarily the one best suited for the application at hand. The FIC, on the other hand, evaluates and ranks candidate models based on the precision of their point estimates of a context‐given focus parameter. This could be any quantity of particular interest, for example, the mean, a correlation, conditional probabilities, or measures of tail dependence. We derive FIC formulae for the maximum likelihood estimator, the two‐stage maximum likelihood estimator, and the so‐called pseudo‐maximum‐likelihood (PML) estimator combined with parametric margins. Furthermore, we confirm the validity of the AIC formula for the PML estimator combined with parametric margins. To study the numerical behavior of FIC, we have carried out a simulation study, and we have also analyzed a multivariate data set pertaining to abalones. The results from the study show that the FIC successfully ranks candidate models in terms of their performance, defined as how well they estimate the focus parameter. In terms of estimation precision, FIC clearly outperforms AIC, especially when the focus parameter relates to only a specific part of the model, such as the conditional upper‐tail probability. 相似文献
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58.
Complex trauma and mental health in children and adolescents placed in foster care: findings from the National Child Traumatic Stress Network 总被引:1,自引:0,他引:1
Greeson JK Briggs EC Kisiel CL Layne CM Ake GS Ko SJ Gerrity ET Steinberg AM Howard ML Pynoos RS Fairbank JA 《Child welfare》2011,90(6):91-108
Many children in the child welfare system (CWS) have histories of recurrent interpersonal trauma perpetrated by caregivers early in life often referred to as complex trauma. Children in the CWS also experience a diverse range of reactions across multiple areas of functioning that are associated with such exposure. Nevertheless, few CWSs routinely screen for trauma exposure and associated symptoms beyond an initial assessment of the precipitating event. This study examines trauma histories, including complex trauma exposure (physical abuse, sexual abuse, emotional abuse, neglect, domestic violence), posttraumatic stress, and behavioral and emotional problems of 2,251 youth (age 0 to 21; M = 9.5, SD = 4.3) in foster care who were referred to a National Child Traumatic Stress Network site for treatment. High prevalence rates of complex trauma exposure were observed: 70.4% of the sample reported at least two of the traumas that constitute complex trauma; 11.7% of the sample reported all 5 types. Compared to youth with other types of trauma, those with complex trauma histories had significantly higher rates of internalizing problems, posttraumatic stress, and clinical diagnoses, and differed on some demographic variables. Implications for child welfare practice and future research are discussed. 相似文献
59.
This paper will provide information on a recent Breakthrough Series Collaborative (BSC) conducted by the National Child Traumatic Stress Network on Using Trauma-Informed Child Welfare Practice to Improve Foster Care Placement Stability. Information on this particular BSC will be provided, followed by initial findings gathered from an evaluation of the BSC and metrics gathered by each of the nine participating teams throughout the BSC process. Specific trauma-informed promising strategies adopted by teams are presented along with recommendations for next steps. 相似文献
60.
Jyh-Jer Roger Ko 《Journal of Labor Research》2003,24(3):473-490
Internal and contingent employment can be either substitutes or complements: Contingent workers are used either to replace
the internal employment system or to complement it. These two perspectives are tested, and the relationship between them is
explored. My findings strongly support the complementary perspective, as the practices usually associated with job security
are positively associated with the use of temporary workers. Above all, internal practices play an important role in deciding
to use contingent employees. My study emphasizes that the institutional employment structure cannot be overlooked when studying
temporary employees. 相似文献