REACTION-TIME ANALYSIS WITH OUTLIER EXCLUSION - BIAS VARIES WITH SAMPLE-SIZE
REACTION-TIME ANALYSIS WITH OUTLIER EXCLUSION - BIAS VARIES WITH SAMPLE-SIZE
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DOI：
10.1080/14640749108400962
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发表时间：
1991-11-01
期刊：
影响因子：
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通讯作者：
MILLER, J
中科院分区：
文献类型：
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作者：
MILLER, J
为了消除虚假的长响应时间的影响，许多研究人员计算“限制性均值”，通过排除任何响应时间超过2.0，2.5或3.0标准差的整体样本平均值。然而，由于反应时间分布是偏斜的，限制平均值的计算引入了偏差：限制平均值低估了反应时间总体的真实平均值。当研究人员在不同观察次数的条件下比较限制均值时，这个问题可能非常严重，因为偏差随着样本量的增加而增加。模拟表明，当将少于10个观测值的条件与多于20个观测值的条件进行比较时，存在显著的差异偏倚。对于强偏态分布和3.0标准差的截止值，差异偏倚可能会影响条件与更多观测值的比较。
To remove the influence of spuriously long response times, many investigators compute "restricted means", obtained by throwing out any response time more than 2.0, 2.5, or 3.0 standard deviations from the overall sample average. Because reaction time distributions are skewed, however, the computation of restricted means introduces a bias: the restricted mean underestimates the true average of the population of response times. This problem may be very serious when investigators compare restricted means across conditions with different numbers of observations, because the bias increases with sample size. Simulations show that there is substantial differential bias when comparing conditions with fewer than 10 observations against conditions with more than 20. With strongly skewed distributions and a cutoff of 3.0 standard deviations, differential bias can influence comparisons of conditions with even more observations.