OG-CR第78题对标准答案异议，大家来讨论下

lysdelyon

原题78. A recent report determined that although only 3
percent of drivers on Maryland highways equipped
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 detectors are more likely to exceed
the speed limit regularly 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
exceeding 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.

标准答案是B


我认为正确答案是D
理由如下：
题目问的结论依靠哪一个assumption？
何谓assumption?即其如果不成立，或者说没有这个前提存在，那么conclusion也就不成立。
3%的司机装了电子狗，33%的超速车是这种装有电子狗的车
得出的结论是装了电子狗的司机比其他司机更可能经常性超速行驶。
如果把问题量化看，马里兰有10000台车，300台装了电子狗（3%）
某天JC上路拦车抓超速，拦了30辆超速车其中有10辆装了电子狗（33%）。
然后写个报告得出结论：装了电子狗的司机比其他司机更可能经常性超速行驶
这结论显然不具代表性，因为取样太少。
如果要扩大代表性，多取样，那么必然要有装了电子狗的超速车多次被抓住超速，才有可能达到33%这个比例，
因此，只有D选项提到这点”许多被罚单的超速车辆在报告调查时期内被罚了不止一次“。
有这个前提假设，conclusion才能够正当成立。


初入GMAT门一个月，请各位前辈指教。

kittycd

我是这样理解这道题的，装雷达--get ticketed--爱超速 是三个独立的东西，题干里说的3%和33%那句话是说明装雷达的好像更容易get ticketed（连接“装雷达”和“get ticketed”）。 接着题干的conclusion就说，装雷达的人好像更容易超速哦~~

所以如果这样理解呢，就可以看出，这里差了一个get ticketed 同爱超速的关系。也可以说，题目把get ticketed 和爱超速等同起来了，但，这不是理所当然的，这是一个assumption。

为啥这个assumption容易被忽略，一个是思维惯性吧，我们可能会习惯于认为被抄牌的人爱超速的人大多数都是重合的，也就是我们习惯上就有这个take for granted 的假设。另外，还有个地方会让你忽略这个地方时，题目中说get ticketed 说的比较详细，说的是get ticketed for 超速，这样一来，我们就更容易把这个“get ticketed for 超速” 跟“爱超速”这个行为方式混起来了。。。。

鄙人愚见，NN们也请看看我这样理解对不对~~~

rebecw

Answer choice D: "ticketed more than once" does not ensure "a more representative sampling." Rather it states that there were repeated offenders on the highway.

Assumption question is different from strengthening question in that the former needs a statement which is necessary for the conclusion to be drawn while the latter simply shed more favorable light on the conclusion.

lysdelyon

明白多拉
谢谢二位

hazardous

B的意思我理解了，但是不知道A为啥不对，谁给讲讲啊

rebecw

When you negate A, you get "Drivers who equip their vehicles with radar detectors are more likely to be ticketed for exceeding the speed limit than are drivers who do not."

And this statement is consistent with one of the premise of the argument, therefore the argument still holds. IF you follow the logic chain of the author and adding the negated choice A), the argument is valid because that's what the author claims!

Whether or not the author's conclusion is right or wrong is not our concern for the assumption-type question. We have to treat the author's statements as correct. Since when you negate A, you do not weaken or refute the author's argument, the argument still holds. Therefore, A) is not the necessary assumption.