一、基本概念 1.定义:它是选择一组能代表所研究疾病特征的患者作为病例组,同时选择一组未患该病但与病例组有可比性的个体作为对照组;用同样的方法调查两组对象过去有无暴露于某种(些)可疑病因的历史及其暴露和程度;通过分 First, the basic concepts 1. Definition: It is to select a group of patients that can represent the characteristics of the disease as a group of patients, while selecting a group of individuals who do not have the disease but comparable to the group of patients as a control group; using the same method To investigate the history and exposure and degree of exposure of two groups of subjects to the suspected cause(s) in the past;