Causation can be inferred by two distinct patterns of reasoning, each requiring a distinct experi-mental design. Common, non-statistical causal inference is associated with controlled experi-ments in basic biomedical research. Statistical inference is associated with Randomized Con-trolled Trials in clinical research. The main difference between the two patterns of inference hinges on the satisfaction of a comparability requirement, which is in turn dictated by the nature of the objects of study, namely homogeneous vs. heterogeneous populations of biological sys-tems. This distinction entails that the objection according to which randomized experiments fail to provide better evidence for causation because randomization cannot guarantee comparability is mistaken. As far as the validity of the statistical inference is concerned, randomization is not re-quired in order to ensure comparability, but rather to prevent systematic bias which may com-promise the accuracy of the intervention.

中文翻译：

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生物医学研究中的因果推断

因果关系可以通过两种不同的推理模式来推断，每种模式都需要不同的实验设计。常见的非统计因果推断与基础生物医学研究中的受控实验有关。统计推断与临床研究中的随机对照试验相关。两种推理模式之间的主要区别取决于对可比性要求的满足，这反过来又由研究对象的性质决定，即生物系统的同质群体与异质群体。这种区别意味着，由于随机化不能保证可比性，因此随机实验不能为因果关系提供更好的证据的反对意见是错误的。就统计推断的有效性而言，