Osborn J F
Department of Epidemiology and Population Science, London School of Hygiene and Tropical Medicine.
Ann Acad Med Singap. 1991 Jan;20(1):95-100.
In the planning of a clinical trial, the statistical aspects of the choice of sample size should be considered. The meaning of statistical terms such as Type I and Type II errors, significance and power are explained. Formulae are given for calculating the required sample size for parallel groups' designs (two independent samples) and matched pair or cross-over designs for both quantitative and qualitative responses. Samples size tables are given with instructions for their use and there are four worked examples. The sample size for a trial depends on the specification of the levels of significance and power and the size of the difference the trial is designed to detect, and these can be somewhat arbitrary. Furthermore, it is often necessary to estimate the standard deviation on the basis of limited information. Thus, the sample size required for a trial cannot be determined precisely, and there can be no exactly right or wrong sample size. However, sensible consideration of sample size should ensure that the trial is not so small as to make the results trivial, nor so large as to be unethical or a waste of resources.
在规划一项临床试验时，应考虑样本量选择的统计学方面。文中解释了诸如I型和II型错误、显著性和检验效能等统计学术语的含义。给出了计算平行组设计（两个独立样本）以及配对或交叉设计中定量和定性反应所需样本量的公式。还给出了样本量表格及其使用说明，并列举了四个实例。一项试验的样本量取决于显著性水平和检验效能的设定以及试验旨在检测的差异大小，而这些设定可能具有一定的随意性。此外，通常需要根据有限的信息来估计标准差。因此，一项试验所需的样本量无法精确确定，不存在绝对正确或错误的样本量。然而，合理考虑样本量应确保试验规模既不会小到使结果无足轻重，也不会大到违背伦理或造成资源浪费。
