临床试验和流行病学调查研究设计总的策略是围绕研究目的试图得到一个有代表性的样本,并获取可靠的研究数据,以保证取得真实性的研究结果。但研究者必须充分认识到,一项试验数据和调查结果可能是以下三方面因素共同作用的一种综合表达。其一,真正由于试验中某一处理因素起的作用,这正是研究 The overall strategy of clinical trials and epidemiological investigations and research designs is to try to obtain a representative sample around the research objectives and obtain reliable research data to ensure that the research results are authentic. However, researchers must fully realize that a test data and survey results may be a comprehensive expression of the following three factors. First, because of the role of a certain treatment factor in the trial, this is precisely the research