Birkett M A, Day S J
Lilly Research Centre Ltd., Windlesham, Surrey, U.K.
Stat Med. 1994;13(23-24):2455-63. doi: 10.1002/sim.4780132309.
We develop the idea of using data from the first 'few' patients entered in a clinical trial to estimate the final trial size needed to have specified power for rejecting H0 in favour of H1 if a real difference exists. When comparing means derived from Normally distributed data, there is no important effect on test size, power or expected trial size, provided that a minimum of about 20 degrees of freedom are used to estimate residual variance. Relative advantages and disadvantages of using larger internal pilot studies are presented. These revolve around crude expectations of the final study size, recruitment rate, duration of follow-up and practical constraints on the ability to prevent the circulation of unblinded randomization codes to investigators and those involved in editing and checking data.
利用临床试验中最初纳入的“少数”患者的数据，来估计若存在真实差异时，为了有特定的把握度拒绝原假设（H0）而支持备择假设（H1）所需的最终试验规模。当比较来自正态分布数据的均值时，只要使用至少约20个自由度来估计残差方差，对检验规模、把握度或预期试验规模就没有重要影响。文中介绍了使用较大内部预试验的相对优缺点。这些优缺点围绕对最终研究规模、招募率、随访持续时间的粗略预期，以及防止未设盲的随机化编码泄露给研究者以及参与数据编辑和核查人员的实际能力限制。
