Walters Stephen J
Medical Statistics Group, School of Health and Related Research, University of Sheffield, Sheffield, UK.
Pharm Stat. 2009 Apr-Jun;8(2):163-9. doi: 10.1002/pst.334.
Pre-study sample size calculations for clinical trial research protocols are now mandatory. When an investigator is designing a study to compare the outcomes of an intervention, an essential step is the calculation of sample sizes that will allow a reasonable chance (power) of detecting a pre-determined difference (effect size) in the outcome variable, at a given level of statistical significance. Frequently studies will recruit fewer patients than the initial pre-study sample size calculation suggested. Investigators are faced with the fact that their study may be inadequately powered to detect the pre-specified treatment effect and the statistical analysis of the collected outcome data may or may not report a statistically significant result. If the data produces a "non-statistically significant result" then investigators are frequently tempted to ask the question "Given the actual final study size, what is the power of the study, now, to detect a treatment effect or difference?" The aim of this article is to debate whether or not it is desirable to answer this question and to undertake a power calculation, after the data have been collected and analysed.
目前,临床试验研究方案的预研究样本量计算是强制性的。当研究者设计一项研究以比较干预措施的结果时,一个关键步骤是计算样本量,以便在给定的统计显著性水平下,有合理的机会(检验效能)检测出结局变量中预先确定的差异(效应大小)。经常会出现研究招募的患者少于初始预研究样本量计算结果所建议的情况。研究者面临这样一个事实,即他们的研究可能没有足够的检验效能来检测预先指定的治疗效果,并且对收集到的结局数据进行的统计分析可能会也可能不会报告具有统计学显著性的结果。如果数据产生了“无统计学显著性结果”,那么研究者经常会忍不住问这样一个问题:“鉴于实际的最终研究样本量,现在该研究检测治疗效果或差异的检验效能是多少?”本文的目的是探讨在数据收集和分析之后回答这个问题并进行检验效能计算是否可取。