Wheeler Matthew W, Park Robert M, Bailer A John
National Institute for Occupational Safety and Health, 4676 Columbia Parkway MS-15, Cincinnati, Ohio 45226, USA.
Environ Toxicol Chem. 2006 May;25(5):1441-4. doi: 10.1897/05-320r.1.
Experimenters in toxicology often compare the concentration-response relationship between two distinct populations using the median lethal concentration (LC50). This comparison is sometimes done by calculating the 95% confidence interval for the LC50 for each population, concluding that no significant difference exists if the two confidence intervals overlap. A more appropriate test compares the ratio of the LC50s to 1 or the log(LC50 ratio) to 0. In this ratio test, we conclude that no difference exists in LC50s if the confidence interval for the ratio of the LC50s contains 1 or the confidence interval for the log(LC50 ratio) contains 0. A Monte Carlo simulation study was conducted to compare the confidence interval overlap test to the ratio test. The confidence interval overlap test performs substantially below the nominal alpha = 0.05 level, closer to p = 0.005; therefore, it has considerably less power for detecting true differences compared to the ratio test. The ratio-based method exhibited better type I error rates and superior power properties in comparison to the confidence interval overlap test. Thus, a ratio-based statistical procedure is preferred to using simple overlap of two independently derived confidence intervals.
毒理学实验人员常常使用半数致死浓度（LC50）来比较两个不同群体之间的浓度-反应关系。这种比较有时是通过计算每个群体LC50的95%置信区间来进行的，如果两个置信区间重叠，就得出不存在显著差异的结论。一种更合适的检验方法是比较LC50的比值与1，或者比较log(LC50比值)与0。在这种比值检验中，如果LC50比值的置信区间包含1，或者log(LC50比值)的置信区间包含0，我们就得出LC50没有差异的结论。进行了一项蒙特卡洛模拟研究，以比较置信区间重叠检验和比值检验。置信区间重叠检验的表现远低于名义显著性水平α = 0.05，更接近p = 0.005；因此，与比值检验相比，它检测真正差异的能力要弱得多。与置信区间重叠检验相比，基于比值的方法表现出更好的I型错误率和更强的检验效能。因此，与使用两个独立得出的置信区间的简单重叠相比，基于比值的统计程序更可取。
