请教一道逻辑题目

bettytons

A recent report determined that although only three percent of drivers on Maryland highways equipped their vehicles with radar detectors, thirty-three percent of all vehicles ticketed for exceeding the speed limit were equipped with them. Clearly, drivers who equip their vehicles with radar detectors are more likely to exceed the speed limit reqularly than are drivers who do not.

The conclusion drawn above depends on which of the following assumptions?

A. Drivers who equip their vehicles with radar detectors are less likely to be ticketed for exceeding the speed limit than are drivers who do not

B. Drivers who are ticketed for exceeding the speed limit are more likely to exceed the speed limit regularly than are drivers who are not ticketed

C. The number of vehicles that were ticketed for ecxeeding the speed limit was greater than the number of vehicles that were equipped with radar detectors

D. Many of the vehicles that were ticketed for exceeding the speed limit were ticketed more than once in the time period covered by the report

E. Drivers on Maryland highways exceeded the speed limit more often than did drivers on other state highways not covered in the report

当时选是选对了B 可做完题反过来推的时候有蒙的不行,请求指点

cattery

最近一个报告显示，虽然只有3%的司机装备了雷达探测器，33%的被罚超速者都装备了雷达探测器。非常清楚，装雷达探测器的司机比未装的司机更可能超速。

原题是通过抓住的超速者的情况，来推出总体上谁比谁更容易超速。这里面就存在一个问题，这些超速者可以真正代表整体超速的情况。

B：如果大多数超速的司机都被没有被抓住，这个结论就不对了。

bettytons

谢谢啊

可是B问题翻译过来是 因超速而被开罚单的司机比超速而未被开罚单的司机更可能经常超速

而题目的意思大体就说装了雷达的司机比没装的更容易经常超速,更容易得罚单

我就晕呼的很啊

iwvers

这个是老外的解释, 虽然看来之后我还是不理解.........寒一个......转不过这个弯.

Evidence:
3% dirvers with radar detectors.
33% of those with radar detectors ticketed for exceeding speed limit.
Conclusion:
Drivers with radar detectors are more likely to exceed the speed limit regularly than driver without….

The only information provided is about the percentage of vehicles equipped with radar and the percentage of ticketed vehicles equipped with radar; the conclusion, however, makes a sweeping generalization about the regular driving behavior of individuals with radar-equipped vehicles.

An as analogy: 'The number of reported laptop thefts on campus increased by 10% from last year to this year. Therefore, more laptops have been stolen from campus this year than last year.'
The assumption here is that REPORTED laptop thefts are meaningfully correlated with ACTUAL laptop thefts. Without this association, the logic falls apart. The same is true for the tickets issued vs. regular speeding in this problem.

cattery

抱歉，是我没有写清楚，重新试一试：

原题：最近一个报告显示，虽然只有3%的司机装备了雷达探测器，但33%的被罚超速者都装备了雷达探测器。非常清楚，装雷达探测器的司机比未装的司机更可能超速。

原题是通过“被抓住的超速者”的情况，来推出“装雷达探测器的司机”比“未装的司机”更可能超速。这里面存在一个概念上的差异，即：“超速司机总体”=“被罚的超速司机”+“未被罚的超速司机”。

B. Drivers who are ticketed for exceeding the speed limit are more likely to exceed the speed limit regularly than are drivers who are not ticketed (for exceeding the speed limit)

被罚的超速司机比未被罚但同样也超速的司机，更容易超速。

“超速司机总体”=“被罚的超速司机”+“未被罚的超速司机”

iwvers

请问LS 牛牛, 如果否定B 的话怎么能够推翻结论呢?

hangtianyuan

原文：被开罚单多---->超速多

B取非：因超速而被开罚单的司机 不比 因超速而未被开罚单司机 有更多的超速
也就是说被开罚单多不代表超速多（推翻原文）

不过这道题不用取非更简单

Avantasia

A recent report determined that although only three percent of drivers on Maryland highways equipped their vehicles with radar detectors, thirty-three percent of all vehicles ticketed for exceeding the speed limit were equipped with them. Clearly, drivers who equip their vehicles with radar detectors are more likely to exceed the speed limit reqularly than are drivers who do not.


3%的司机装了雷达探测；
33%的汽车被抓住超速；


司机跟汽车（的所有者，即安装设备的人）不见得有关系。所以要假设
1. 在超速的时候，每个司机都开他/她自己的车
或者
2. 装了雷达探测的司机不管开什么车都很快。


所以答案是B

peter3008

这道题目也困扰我很久了，我后来尝试用数学的极限方法去解题，希望给大家一点brain storm.
文中有4个要素：（1）。radar (2).超速，(3) 开罚单,(4) 不开罚单但超速了，其中(2)=(3)+(4)
前提：（1）在(2),(3)中的比例高 （装了radar容易超速开罚单）
结论：（1）容易超速（2） （装radar容易超速）

只有当（2）和（3）是同一个概念的时候，或者说在数量上一样的话，前提跟结论相一致，（2）=（3）+（4），用极限的思维，当（3）比（4）多很多很多的时候，就近似（2）=(3), 在数量上一致。那么前提跟结论也就一致了。也就是说，超速的人数等于开罚单的人数，即所有超速的人都被开了罚单，无一幸免。

PS: 这里有个逻辑条件： 开罚单的一定是超速了 （罚单—〉超速），但是超速不一定开罚单，所以要素4是隐含的，如果忽略要素4，直接说（2）=（3）也就可以了。

“引用别的论坛上一位DD的解释“
“其实差不多的意思
前半部分是：有雷达探测器的车比没有雷达探测器的车更容易得到超速罚单
结论是    ：有雷达探测器的车比没有雷达探测器的车更容易经常超速

如果形成的假设是得到超速罚单的车更容易经常超速，不就形成结论了嘛，很清晰”