Investigating the effects of ties on measures of concordance
Investigating the effects of ties on measures of concordance
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DOI：
10.1002/sim.3257
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发表时间：
2008-09-20
影响因子：
2
通讯作者：
Greene, Tom
中科院分区：
文献类型：
--
作者：
Yan, Guofen;Greene, Tom
预测结果和观察结果之间的一致性，称为C指数或C统计量，经常用于量化预后模型的判别能力。它通常也作为区分不同模型之间预测强度的基础。C指数的两种替代公式被广泛使用。一个从计算中完全排除关系（C-tied.out），另一个包括关系（C-tied. in）。然而，很少有研究关系对这两个措施的影响。在本文中，我们描述了C-tied.in和C-tied.out的性能变化，逐渐减少粗糙（或更粗糙）的数据分区。我们的理论和模拟结果表明，这两种措施可以在很大程度上依赖于捆绑对的数量，他们的结果可以是实质性的分歧。我们研究潜在的歧义，可能会发生时，这两个措施dive-e。在存在相当大比例的捆绑对的情况下，我们建议将C索引计算为下限和上限，并且。在可行的情况下。应该针对与被比较的模型的相同序列相对应的分区来计算C索引。当需要一致性时，也可以考虑两个C指数的平均值。我们估计超过。C使用血液透析临床试验的数据来说明我们的评估和方法。版权所有（C）2008约翰威利父子有限公司
The concordance between predicted and observed outcomes, referred to as the C index or C statistic, is frequently Used to quantify the discriminatory ability of a prognostic model. It also commonly serves as a basis for distinguishing predictive strength between different models. Two alternative formulations of the C index are widely Used. one completely excluding ties from the computation (C-tied.out) and the other including ties (C-tied.in). However, there has been little research concerning the effects of ties on these two measures. In this paper we characterize changes in the performance of C-tied.in and C-tied.out for progressively less coarse (or more coarse) partitions of the data. Our theoretical and simulation results show that both measures can be heavily dependent on the number of tied pairs and their results can be substantially divergent. We examine potential ambiguities that can occur when the two measures diver-e. In the presence of a substantial proportion of tied pairs, we recommend that both C indices be computed as lower and Upper bounds, and that. when feasible. the C indices should be computed with respect to partitions corresponding to the same percentiles for the models being compared. When it is desired to all concordance, the average value of the two C indices might also be considered. We estimate the over. C Use the data from the Hemodialysis Clinical Trial to illustrate our evaluation and methods. Copyright (C) 2008 John Wiley & Sons, Ltd.