论文部分内容阅读
概率的运算与疾病筛检、计量诊断、统计决策等都有密切的联系。我们在第二讲介绍过一些关于事件、集合、不相容事件的概率加法等基本概念。现在进一步介绍概率的运算规则。1 条件概率与乘法定理某一事件在特定条件下发生的概率称为该事件的条件概率。例如:“在食堂用餐者的腹泻率”,指的是在食堂用餐这一事件发生的条件下腹泻的发病率。用A代表“在食堂用餐”这一事件,B表示“腹泻”,则上述条件概率可记作P(B|A)=在食堂用餐并腹泻的人数/在食堂用餐的人数=A与B同时发生的次数/A发生的次数(1) 如果事件A的发生与事件B无关,换言之,若A与B独立,则P(B|A)=P(B) P(A|B)=P(A)
The calculation of probability is closely related to disease screening, measurement diagnosis, and statistical decision-making. In the second lecture, we introduced some basic concepts such as the addition of probability, collection, and inconsistent events. Now introduce the rules of probability operation. 1 Conditional probability and multiplicative theorem The probability of an event occurring under a specific condition is called the conditional probability of the event. For example: “The diarrhea rate of the diners in the cafeteria” refers to the incidence of diarrhea in the event of eating in the cafeteria. With A representing “dining in the canteen” and B representing “diarrhea”, the above conditional probability can be recorded as P(B|A) = number of people dining in the cafeteria and diarrhea / number of people dining in the canteen = A and B Number of Occurrences/Number of Occurrences of A (1) If Event A occurs independently of Event B, in other words, if A and B are independent, then P(B|A)=P(B) P(A|B)=P ( A)