Experimental balance is usually understood as the control for the value of the conditions, other than the one under study, which are liable to affect the result of a test. We discuss three different approaches to balance. ‘Millean balance’ requires identifying and equalizing ex ante the value of these conditions in order to conduct solid causal inferences. ‘Fisherian balance’ measures ex post the influence of uncontrolled conditions through the analysis of variance. In ‘efficiency balance’ the value of the antecedent conditions is decided ex ante according to the efficiency they yield in the estimation of the treatment outcome. Against some old arguments by Worrall, we show that in both Fisherian and efficiency balance there are good reasons to randomize the allocation of treatments, in particular when there is no agreement among experimenters as to the antecedent conditions to be controlled for.

中文翻译：

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为什么实验平衡仍然是随机化的一个原因

实验平衡通常被理解为对除所研究的条件之外的条件值的控制，这些条件容易影响测试结果。我们讨论三种不同的平衡方法。 “米尔平衡”要求事前识别和平衡这些条件的价值，以便进行可靠的因果推论。 “费希尔平衡”通过方差分析事后衡量不受控制条件的影响。在“效率平衡”中，先行条件的值是根据它们在估计治疗结果时产生的效率而预先决定的。针对沃勒尔的一些旧论点，我们表明，在费舍尔平衡和效率平衡中，都有充分的理由随机分配治疗，特别是当实验者之间对于要控制的先行条件没有达成一致时。