combination method

  • 文章类型: Journal Article
    流感季节的特点每年有很大差异,对公共卫生准备和应对构成挑战。流感预测用于通知季节性爆发反应,这反过来又有可能减少流行病的影响。美国疾病控制和预防中心,与外部研究人员合作,进行了年度前瞻性流感预测工作,被称为FluSight挑战。将预测文献的理论结果与流感爆发的特定领域预测相结合,我们应用参数预测组合方法,同时优化模型权重,并通过β变换校准集合,并对方法进行调整,以降低其复杂性。我们使用了β变换线性池,有限β混合模型,以及他们的等权重调整,以对美国2016/2017、2017/2018和2018/2019流感季节进行回顾性预测我们将它们的性能与FluSight挑战中使用的方法进行了比较,以产生FluSight网络集成,即平均加权线性池和线性池。根据平均对数分数,在测试季节中,通过采用beta变换的方法产生的集合预测在所有一周前目标中都优于同等加权线性池和线性池的预测。尽管在所有目标和季节中都采用了β转换的线性池或β混合方法,但我们观察到总体准确性的提高。应考虑对线性汇集中的已知校准问题进行明确调整的组合技术,以提高爆发设置中的概率得分。
    The characteristics of influenza seasons vary substantially from year to year, posing challenges for public health preparation and response. Influenza forecasting is used to inform seasonal outbreak response, which can in turn potentially reduce the impact of an epidemic. The United States Centers for Disease Control and Prevention, in collaboration with external researchers, has run an annual prospective influenza forecasting exercise, known as the FluSight challenge. Uniting theoretical results from the forecasting literature with domain-specific forecasts from influenza outbreaks, we applied parametric forecast combination methods that simultaneously optimize model weights and calibrate the ensemble via a beta transformation and made adjustments to the methods to reduce their complexity. We used the beta-transformed linear pool, the finite beta mixture model, and their equal weight adaptations to produce ensemble forecasts retrospectively for the 2016/2017, 2017/2018, and 2018/2019 influenza seasons in the U.S. We compared their performance to methods that were used in the FluSight challenge to produce the FluSight Network ensemble, namely the equally weighted linear pool and the linear pool. Ensemble forecasts produced from methods with a beta transformation were shown to outperform those from the equally weighted linear pool and the linear pool for all week-ahead targets across in the test seasons based on average log scores. We observed improvements in overall accuracy despite the beta-transformed linear pool or beta mixture methods\' modest under-prediction across all targets and seasons. Combination techniques that explicitly adjust for known calibration issues in linear pooling should be considered to improve probabilistic scores in outbreak settings.
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  • 文章类型: Journal Article
    Plants with alien genomic components (alien chromosomes / chromosomal fragments / genes) are important materials for genomic research and crop improvement. To date, four strategies based on trait observation, chromosome analysis, specific proteins, and DNA sequences have been developed for the identification of alien genomic components. Among them, DNA sequence-based molecular markers are mainly used to identify alien genomic components. This review summarized several molecular markers for identification of alien genomic components in wheat, cabbage and other important crops. We also compared the characteristics of nine common molecular markers, such as simple sequence repeat (SSR), insertion-deletion (InDel) and single nucleotide polymorphism (SNP). In general, the accuracy of using a combination of different identification methods is higher than using a single identification method. We analyzed the application of different combination of identification methods, and provided the best combination for wheat, brassica and other crops. High-throughput detection can be easily achieved by using the new generation molecular markers such as InDel and SNP, which can be used to determine the precise localization of alien introgression genes. To increase the identification efficiency, other new identification methods, such as microarray comparative genomic hybridization (array-CGH) and suppression subtractive hybridization (SSH), may also be included.
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  • 文章类型: Comparative Study
    In multi-arm adaptive trials, several treatments are assessed simultaneously and accumulating data are used to inform decisions about the trial, such as whether treatments are dropped or continued. Different methodological approaches have been developed for such trials and research has compared the performance of different subsets of these. One particular approach, for which we use the acronym MAMS(R), has generally not been included in these comparisons because control of the family-wise error rate (FWER) could not be guaranteed. Recently, the MAMS(R) approach has been extended to facilitate the generation of efficient designs which strongly control the FWER. We consider multi-arm two-stage trials with binary outcomes and propose parameterising treatment effects using the log odds ratio. We conduct a simulation study comparing the extended MAMS(R) framework with the well-established combination method both for trials where a different outcome is used for mid-trial analysis and for trials where the same outcome is used throughout. We show how the MAMS(R) framework compares favourably only in scenarios where the same outcome is used. We propose a hybrid selection rule within MAMS(R) methodology and demonstrate that this makes it possible to use the MAMS(R) framework in trials incorporating comparative treatment selection.
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