Stampfer M J, Buring J E, Willett W, Rosner B, Eberlein K, Hennekens C H
Stat Med. 1985 Apr-Jun;4(2):111-6. doi: 10.1002/sim.4780040202.
The 2 x 2 factorial design calls for randomizing each participant to treatment A or B to address one question and further assignment at random within each group to treatment C or D to examine a second issue, permitting the simultaneous test of two different hypotheses. This design can increase the efficiency of large-scale clinical trials. The Physicians' Health Study, a randomized trial of aspirin and beta-carotene among U.S. physicians, illustrates some features and potential problems in the design and analysis of a factorial trial. The most common concern, interaction between treatments, is generally an advantage rather than a limitation of this design. Although such interactions are relatively uncommon, this design provides a means to measure an effect which otherwise might not be apparent. If the interaction is sufficiently severe, however, then loss of power is possible.
2×2析因设计要求将每个参与者随机分配到治疗A或治疗B以解决一个问题，并在每组中进一步随机分配到治疗C或治疗D以研究另一个问题，从而允许同时检验两个不同的假设。这种设计可以提高大规模临床试验的效率。医师健康研究是一项针对美国医师进行的阿司匹林和β-胡萝卜素的随机试验，它说明了析因试验设计和分析中的一些特点及潜在问题。最常见的问题，即治疗之间的相互作用，通常是这种设计的一个优点而非局限性。虽然这种相互作用相对不常见，但这种设计提供了一种测量否则可能不明显的效应的方法。然而，如果相互作用足够严重，那么可能会出现检验效能的损失。
