Understanding and misunderstanding randomized controlled trials.
Understanding and misunderstanding randomized controlled trials.
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理解和误解随机对照试验。
DOI：
10.1016/j.socscimed.2017.12.005
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发表时间：
2018-08
期刊：
影响因子：
--
通讯作者：
Cartwright N
中科院分区：
文献类型：
--
作者：
Deaton A;Cartwright N
随机对照试验（RCT）在社会科学中越来越受欢迎，而不仅仅是在医学领域。我们认为，外行公众，有时研究人员，把太多的信任在随机对照试验的其他方法的调查。与应用文献中常见的说法相反，随机化并不能使治疗组和对照组中除治疗外的所有内容相等，它不能自动提供平均治疗效应（ATE）的精确估计，并且它不能减轻我们考虑（观察到的或未观察到的）协变量的需要。确定一个估计值是否是偶然产生的，比通常认为的要困难得多。最好的情况下，RCT产生无偏估计，但该属性的实用价值有限。即使这样，估计数也只适用于为试验选定的样本，往往只是一个方便的样本，并且需要有理由将结果扩展到其他群体，包括试验样本所属的任何群体，或任何个人，包括试验中的个人。要求“外部效度”是没有帮助的，因为它对RCT的期望太高，同时低估了它的潜在贡献。RCT确实需要最少的假设，并且可以在几乎没有先验知识的情况下操作。在说服不信任的听众时，这是一个优势，但对于累积的科学进步来说，这是一个劣势，在这种情况下，应该建立在先前知识的基础上，而不是抛弃。随机对照试验可以在建立科学知识和有用的预测方面发挥作用，但它们只能作为累积计划的一部分，与其他方法结合，包括概念和理论发展，以发现“什么有效”，但“为什么事情有效”。
Randomized Controlled Trials (RCTs) are increasingly popular in the social sciences, not only in medicine. We argue that the lay public, and sometimes researchers, put too much trust in RCTs over other methods of investigation. Contrary to frequent claims in the applied literature, randomization does not equalize everything other than the treatment in the treatment and control groups, it does not automatically deliver a precise estimate of the average treatment effect (ATE), and it does not relieve us of the need to think about (observed or unobserved) covariates. Finding out whether an estimate was generated by chance is more difficult than commonly believed. At best, an RCT yields an unbiased estimate, but this property is of limited practical value. Even then, estimates apply only to the sample selected for the trial, often no more than a convenience sample, and justification is required to extend the results to other groups, including any population to which the trial sample belongs, or to any individual, including an individual in the trial. Demanding ‘external validity’ is unhelpful because it expects too much of an RCT while undervaluing its potential contribution. RCTs do indeed require minimal assumptions and can operate with little prior knowledge. This is an advantage when persuading distrustful audiences, but it is a disadvantage for cumulative scientific progress, where prior knowledge should be built upon, not discarded. RCTs can play a role in building scientific knowledge and useful predictions but they can only do so as part of a cumulative program, combining with other methods, including conceptual and theoretical development, to discover not ‘what works’, but ‘why things work’.
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