Fisher, Bradford Hill, and randomization
Fisher, Bradford Hill, and randomization
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DOI：
10.1093/ije/dyg286
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发表时间：
2003-12-01
影响因子：
7.7
通讯作者：
Armitage, P
中科院分区：
文献类型：
--
作者：
Armitage, P
925明显合理的方法，避免分配偏差，如交替。他后来强调了这一区别，并在链霉素治疗肺结核的试验和百日咳疫苗的试验中实践了这一方法。现在让我们更详细地看看这两个人给出的随机化的原因。我们应该认识到，费舍尔能够在比希尔强得多的组织支持下进行受控实验。几十年来，洛桑斯特德一直是田间试验的所在地，他在20世纪20年代的同事们不需要说服就知道需要同时进行对照比较。他们知道不应该比较不同田地的肥料，也不应该比较一个特定的品种和前一年的另一个品种。唯一的问题是如何将处理分配给地块。相比之下，在20世纪30年代后期，医学上的对照试验还远没有得到保障。当然，人们听到了对林德等"公平"比较先驱的赞扬，但也有人提倡历史比较，或认为控制分配忽视了个人的独特性，可能是不道德的。因此，希尔既要说明同时控制的一般情况，又要说明随机化的具体情况。Fisher反复且一致地给出了相同的随机化理由。在19263年他写道：一种方法，以确保一个有效的估计误差将获得的是安排情节故意随机，使没有区别可以蠕变之间的情节对处理一样，对不同的待遇;在这种情况下，估计误差，来自通常的方式变化的一套情节处理一样，可适用于测试的意义所观察到的差异的平均值的情节处理不同。
925 apparently reasonable methods of avoiding allocation bias, such as alternation. He emphasized the distinction later and was able to put the method into practice in the trial of streptomycin in pulmonary tuberculosis and in the trial of pertussis vaccines planned earlier but published later. Let us now look in more detail at the reasons for randomization given by these two men. We should realize that Fisher was able to approach controlled experimentation with much stronger organizational support than Hill. Rothamsted had been the home of field trials for many decades, and his colleagues in the 1920s needed no persuasion of the need for simultaneous controlled comparisons. They knew better than to compare fertilizers on different fields, or to compare a particular variety one year with another variety in the previous year. The only question was how to allocate treatments to plots. By contrast, the case for controlled trials in medicine was far from secure in the late 1930s. Voices were certainly heard in praise of the pioneers of ‘fair’comparisons, such as Lind, but others advocated historical comparisons or argued that controlled allocation ignored the uniqueness of the individual and was perhaps unethical. So Hill had to make the general case for simultaneous control as well as the more specific case for randomization. Fisher repeatedly and consistently gave the same justification for randomization. In 19263 he wrote:One way of making sure that a valid estimate of error will be obtained is to arrange the plots deliberately at random, so that no distinction can creep in between pairs of plots treated alike and pairs treated differently; in such a case an estimate of error, derived in the usual way from the variation of sets of plots treated alike, may be applied to test the significance of the observed difference between the averages of plots treated differently.