[求教]OG12 78超速吃罚单-大家总是解释为何选B，没有具体说明为何不选A

nightingale

Q78.

A recent report determined that although only 3 percent of drivers on Maryland highways equipment their vehicles with radar detectors, 33 percent of all vehicles ticketed for exceeding the speed limit were equipped with them. Clearly, drivers who equip their vehicles with radar detecters are more likely to exceed the speed limit regularly than are drivers who do not.

the conclusion drawn above depends on which of the assumotions?

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 likely to exceed the speed limit reguarly than are drivers who are not ticketed.
C The number of vehicles that were ticketed for exceeding the speed limit was greater than the number of vehicles that were equipped with radar detectors.
D Many of the vehicels that were ticketed for exceeding the speed limit wre located more than once in the time period covered by the report.
E Drivers on Maryland highways exceeded the speed limit more often than diDd drivers on other state highways not covered in the report

首先我支持B选项可以说明问题，是符合题意的。但是请问A选项错在哪里呢？

如果说装了雷达的车更不容易因为超速而吃罚单，那结合题中条件，装了雷达的车吃了更多罚单，不是更应该证明装了雷达的车超速的次数比不装的车多得多么？
OG的解释是这个选项针对吃罚单的问题可能是真的，但与题中关于经常超速的问题不相关。我怎么觉得这个解释有点牵强呢？因为选项明明说的是are less likely to be ticketed for exceeding the speed limit，不是已经和超速联系起来了么？难道就是因为没有明确说在“相同次数”的超速情况下不容易吃罚单么？我怎么觉得这个思维还是不对呢？

希望大家理解了这个选项错误原因的给予解释。
谢谢！

nightingale

因为超速吃罚单机率小+实际吃罚单多，不是更加可以推出实际超速多么？

我知道B是正着推的，很顺。
可是A可以逆着推啊，感觉也不无道理。

nightingale

有人帮忙解释一下不？

nightingale

LS, thank you very much for your explanation, but I am afraid I cannot agree that we need to follow the logic chain of the author just because that's what the author claims.

The CR question asked "the conclusion drawn above depends on which of the assumptions", which means the assumption we selected cannot be ignored when getting the conclusion.  Without this assumption, there will be a gap between the premise and the conclusion of the argument.  In other words, if only based on the words provided in the argument, there is no "LOGIC" train.

Correct me if I am wrong.

Anyway, you provided a new point which I have not considered before.  Thanks very much, sdcar2010.

nightingale

Still a little confused, but I noticed one difference between A and B.

If we negate A, the argument might hold or not.
If we negate B, the argument definately cannot hold.

It is the difference between the sufficiency and necessity.
So can we say that the assumption this question required is a necessary condition, rather than a sufficient evidence, to reach the conclusion?

nightingale

I finally found an instruction from lawyer:
"一。ASSUMPTION类。假设类分充分型和必要型。充分型是问题问你下列哪个假设，能使原文的结论PROPOERLY推出。必要型是问题问你原文的推理依赖下列哪个假设。他们的作题思路不同。充分类因为原文结论是必须能从证据推出（加上假设），所以方法较简单，将选项加到原文的推理中，如果结论必成立（MUST BE），则为答案，如果结论有不成立的可能性，则错，其中的特例是原文证据和结论的概念差异（GAP），说出这个GAP就是假设。必要类复杂点，总体的方法是将选项取非，如果原文的结论必不成立，则为答案，如果还有成立的可能性，则错。取非就是假设选项是错的。其中有几种特例。一是其他类（其他原因，可能性。。。），它的假设是不存在其他（原因，可能）。另一种是原文证据和结论的概念差异（GAP），说出这个差异就是假设。还有一种是只考虑单方面，其假设是其他方面没影响。其特例是比较两个东东，只比较某方面，便得出一个总体结论，其假设是其他方面没影响。充分类的加进法和必要类的取非法都可用于TEST所有选项，但因时间较长，所以通常方法是用有关无关排除后剩下难分的选项才用这方法，很多情况下通过有关无关排除便只剩下一个。他们的特例则可以直接找答案。"

As I said, I think CR 78 belongs to 必要型.

The next question is, how to differentiate 充分型 and 必要型?

nightingale

Show me your reasoning why after negating A, the argument might not hold.

Remember, no outside assumptions or opinions.  Just follow the logic presented in the stimulus.

-- by 会员 sdcar2010 (2011/3/6 1:59:04)

Say, we have 100 drivers, 3 of them equipped their vehicles with radar detectors (we call them RD), and 97 did not (we call them NRD).  Each driver drives exceeding the speed limite 11 times during the report period.  As we negating A, RD are more likely to be tiketed than NRD, so it is possible that the 11 times for the 3 RD are all tiketed, while the 11 times for the 97 NRD are only ticketed for 67 times in total.  Then the report showed that 33% tiketed vehicles are all equipped with radar detector.  Under this condition, we cannot get the conclusion that RD are more likely to exceed the speed limit regularly than NRD, since the times they do during a certain period are the same.

This is an extreme example, though.  But we can see from this that the conclusion "might" not hold.
This is also why I said, without the assumption the question is asking, the argument itself is not logical.

nightingale

Oh, LS, use greaterer numbers, 300 RD and 9700 NRD with one exceed each.  Still, 33 of RD and 67 of NRD are ticketed.  Then we can solve the "over and over" problem.

The theme here is that the conclusion might not hold.

nightingale

It is not my premise/assumption.  It is just an example of possible condition to show that when the premises of the questions are met (3% and 33%), the conclusion (more regularly) might not hold.

As I said, I already know the difference between A and B, based on lawyer's theory.
It is just another question I need to figure out: when the question is 充分型, and when it is 必要型.
If you would like, we can move on.

nightingale

As to "when the question is 充分型, and when it is 必要型.", the former is justifying assumption while the latter is necessargy assumption.

Necessary: depend on, rely on, need, require, must-be-true.

-- by 会员 sdcar2010 (2011/3/6 22:57:24)

Thanks very much, sdcar.
Do we have any key words for the justifying assumption? or just without the ones for necessary assumption, the question type should be justifying assumption?