在线等，请教大家

tangyunjie

When 100 people who have not used cocaine are tested for cocaine use, on average only 5 will test positive. By contrast, of every 100 people who have used cocaine 99 will test positive. Thus, when a randomly chosen group of people is tested for cocaine use, the vast people is tested for cocaine use, the vast majority of those who test positive will be people who have used cocaine.


A reasoning error in the argument is that the argument


A.attempts to infer a value judgment from purely factual premises
B.attributes to every member of the population the properties of the average member of the population
C.fails to take into account what proportion of the population have used cocaine
D.ignores the fact that some cocaine users do not test positive
E.advocates testing people for cocaine use when there is no reason to suspect that they have used cocaine
答案是C，但是我觉得B不是也有道理吗

sunshengkun666

这道题是这样的，没使用过C的人基本不呈阳性，使用过C的人基本呈阳性，所以题目说随机做测试，呈阳性的就是用过药的。
这是有漏洞的，因为不知道随机抽取的人中使用过C的人的比例和未使用过C的人的比重。比如说，假如未使用C的人占99%，则那么99%*5%也大于1%*99%

zoemiaoer

题目说By contrast, of every 100 people who have used cocaine 99 will test positive。那么着100使用过Cocaine的人占总人数的多少呢？否则这个100人就没有参考性，所以选择B

shencangbulu

我觉得B选项很绕,楼主觉得这句话的中文意思是什么呢?attribute to是归因于的意思.

原文的主要的问题是样本采集的范围是未知的.一个很小的百分比在一个很大的pool里,可能它的绝对值要大于一个很大的百分比在一个很小的pool里