Inference by eye: Reading the overlap of independent confidence intervals
Inference by eye: Reading the overlap of independent confidence intervals
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DOI：
10.1002/sim.3471
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发表时间：
2009-01-30
影响因子：
2
通讯作者：
Cumming, Geoff
中科院分区：
文献类型：
--
作者：
Cumming, Geoff
当独立平均值的95%置信区间（CI）不重叠时，双尾p值小于0.05，平均值之间存在统计学显著差异。然而，对于不重叠的95% CI，p实际上远小于0.05：117两个CI刚好接触，p约为0.01，并且在p变得大到0.05之前，间隔可以重叠大约一个CI臂长度的一半。记住这条规则，即一个臂的一半长度的重叠大约对应于p=0.05时的统计学显著性，这有助于快速了解显示CI的图，特别是在没有报告精确p值的情况下。作者研究了这一规则和类似规则的稳健性，发现当样本量至少为10时，它们足够准确，并且两个区间的宽度相差不超过2倍。作者回顾了之前关于CI重叠的讨论，并将研究扩展至p值0.05和0.01以外的其他值。他还研究了两个比例和两个皮尔逊相关系数的95% CI，并发现类似的规则适用于这些非对称CI的重叠，适用于非常广泛的情况。最好更广泛地使用具有95%置信区间的数字，这些规则可能有助于容易和适当地理解这些数字。版权所有（C）2008约翰威利父子有限公司
When 95 per cent confidence intervals (CIs) on independent means do not overlap, the two-tailed p-value is less than 0.05 and there is a statistically significant difference between the means. However, p for non-overlapping 95 per cent CIs is actually considerably smaller than 0.05: 117 the two CIs just touch, p is about 0.01, and the intervals can overlap by as much as about half the length of one CI arm before p becomes as large as 0.05. Keeping in mind this rule-that overlap of half the length of one arm corresponds approximately to statistical significance at p=0.05-can be helpful for a quick appreciation of figures that display CIs, especially if precise p-values are not reported. The author investigated the robustness of this and similar rules, and found them sufficiently accurate when sample sizes are at least 10, and the two intervals do not differ in width by more than a factor of 2. The author reviewed previous discussions of CI overlap and extended the investigation to p-values other than 0.05 and 0.01. He also studied 95 per cent CIs on two proportions, and on two Pearson correlations, and found similar rules apply to overlap of these asymmetric CIs, for a very broad range of cases. Wider use of figures with 95 per cent CIs is desirable, and these rules may assist easy and appropriate understanding of such figures. Copyright (C) 2008 John Wiley & Sons, Ltd.