偏倚bias-吉林大学.ppt

我们的担心没有了，于是又把夜灯打开了，皆大欢喜 控制混杂的方法 研究设计阶段 随机化 限制 匹配 资料分析阶段 分层分析 多变量分析 主要内容 概述 设计与实施 资料分析 常见偏倚与控制 优缺点 优缺点 适合于对病因复杂、发病率低、潜伏期长的疾病进行研究，有时是罕见病病因学研究的唯一选择； 病例对照研究所需样本量小，因此工作量不大，节省人力、物力，易于进行，出结果快； 适用于多种暴露因素与某一种疾病的关联研究； 可以对防治措施的疗效与不良反应作用做出初步的评价。 优 点 不适用于人群中暴露比例很低的因素； 易发生各种偏倚； 难以确定暴露与疾病的先后顺序，无法直接得出因果结论； 不能计算暴露与无暴露人群的发病率，只能估计相对危险性。 缺 点 思考题 病例对照研究的基本原理与特点？ 对照组选择的基本原则？ 匹配的目的？ 比值比（OR） 病例对照研究与队列研究的优缺点比较？ 成组资料与配对资料的分析？ 何谓偏倚？主要有哪几种类型？ * * * * Let’s look at another example. Here is a picture of my daughter, Sonia, with her Winnie the Pooh nightlight. We found having this nightlight was very helpful to us when it came to navigating around her room at night. * We kept the nightlight on until we read the now famous study in Nature from my Alma Mater, the University of Pennsylvania, which strongly suggested that ambient nighttime lighting before age 2 was associated with the occurrence of nearsightedness in children. Here kids who used nightlights were over 3 times more likely to have myopia. * So, off went the nightlight and we began to stumble around her room. * Until two subsequent studies came out, again in Nature, showing no association. * These authors believed that the apparent association use of a night light and child’s myopia was likely because of confounding by parent’s myopia. These authors provided direct data that nearsightedness in parents is associated with the use of night light, probably to help the parents see better. And, there is data to suggest that myopia is inherited; ie if parents have it, their kids are more likely to have it. So, this is an example, where parenteral myopia confounds the relationship between night lights and child’s myopia and there is no real direct, or what we call independent, association between use of night lights and child’s myopia. * So, our fears relieved about night lights. . .. on comes the night light again and everyone is happy. * * 分层分析 EpiCalc 2000 分层分析 EpiCalc 2000 资料分析步骤 整理四格表 ?2检验 计算OR及其可信区间 分层分析 OR=2.20 (1.25~3.86) 考