Clinical trials take a long time because they're rigorously controlled, with close attention paid to sampling bias and methodology.
临床试验需要花费很长时间，因为它们处于严格控制之下，必须密切留意取样偏差与方法。
Self-selection bias and sampling bias are also discussed at the end of the paper.
与此相关的自选择偏差和抽样偏差问题也在文中进行了讨论。
Self-selection bias and sampling bias are also discussed at the end of the paper.
与此相关的自选择偏差和抽样偏差问题也在文中进行了讨论。
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