关于og12 cr78超速吃罚单的题，小弟再次遇到又研究了一下，试着解释解释，求各牛拍砖

sdcar2010

1、关于对结论（1）部分的论证：
我认为如果要有（1）这样的结论，一定 是比较  （x*超速车)/（3%*总车)  与 【（1-x)*超速车】/（97%*总车)  才能得到的------------x是超速车中安装了radar的比例
但是，如果按照你的理解把“被ticket车”和“超速车”分开，那么x就永远未知，也就永远无法得出（1）中的结论，也就得不出整体结论。

Wrong. You still do not understand the difference between sufficient assumption and necessary assumption.

There are many roads to Rome.  Some of them are the ONLY road (necessary). But using these roads ALONE cannot be sufficient for one to get to Rome.  Nonetheless, these necessary roads are INDISPENSABLE.

Akin to the above analogy, a necessary assumption for the passage is indispensable for the conclusion to be drawn, but may not be sufficient when used alone to reach the final conclusion.

Once you understand the above explanation, you will understand why what you presented was wrong.

A rule of thumb: For a necessary assumption, the language is not strict, but broad and general, to cover many possible alternatives.
For a sufficient assumption, the language is strict and narrow, to narrow down to a single enabling scenario.

According to the passage, the numbers of 3% and 33% are just two numbers. The passage does not say both was obtained from the same "study."  In fact the words like study or poll or the like are not mentioned in the passage!  Like I said, both numbers are not from a STUDY with ALL the cars during a specific checkout period.  If in doubt, ask a Chinese policeman for details.

Your equation is specific, requires A LOT of assumptions, thus, it may be sufficient, but not necessary.

pirate舟

According to the passage, the numbers of 3% and 33% are just two numbers. The passage does not say both was obtained from the same "study."  In fact the words like study or poll or the like are not mentioned in the passage!  Like I said, both numbers are not from a STUDY with ALL the cars during a specific checkout period.  If in doubt, ask a Chinese policeman for details.
在这个题目当中，你的这个说法很有道理，如果我承认确实被ticket的车和超速的车不能看成一致的。
那么我不能理解的是，我们要如何从题目和B)中推出“有r的车比没r的车更可能超速” 这个结论，如果我们把regularly先抛开的话？


Your equation is specific, requires A LOT of assumptions, thus, it may be sufficient, but not necessary.
我的理解是，这个equation确实不是necessary，但是就题目的条件来看，这是我唯一可以推想的方向了，还是回到那个问题，我不知道要如何用题目条件+B)选项得出“有r的车比没r的车更可能超速” 这个说法？

sdcar2010

Necessary assumption. Use negation.

If you negate (B), you have:
Drivers who are ticketed for exceeding the speed limit are NOT more likely to exceed the speed limit regularly than are drivers who are not ticketed.

If that is the case, then for those drivers who have radar detectors and who got a speeding ticket, they are NOT more likely to exceed the speed limit regularly than are drivers who are not ticketed. This is in contrary to the conclusion of the stimulus -- Drivers who equip their vehicles with radar detectors ARE more likely to exceed the speed limit regularly than are driver who do not. So if you negate (B), the stimulus falls apart. Thus, (B) is the correct answer since it is necessary for the conclusion to be drawn.

pirate舟

两个问题：
1、Drivers who are ticketed for exceeding the speed limit are NOT more likely to exceed the speed limit regularly than are drivers who are not ticketed. ------>for those drivers who have radar detectors and who got a speeding ticket, they are NOT more likely to exceed the speed limit regularly than are drivers who are not ticketed.
Why? how did you bring the factor 'radar' inside this discuss?


2、So if you negate (B), the stimulus falls apart.
你这里的stimulus falls apart 具体指什么？是stimulus和conclusion falls apart吗？stimulus从来就没有和conclusion有过完整的逻辑联系呀。我想知道在你的整个推理过程中，是怎么运用题目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，这个条件的

sdcar2010

1) In the stimulus: 33 percent of all vehicles ticketed for exceeding the speed limit were equipped with them. Therefore, 33% of those ticketed do have radar.
Since you like math, here comes the math:  A = A1 + A2.  If A is NOT more likely than B to do something and A comprises A1; then A1 is DEFINITELY not more likely than B to do something!  That's called proper deduction.

2) stimulus = passage.

As to how to use the two cited numbers and reach the original conclusion in the passage (stimulus), that is not my concern because that is asking for an enabling condition to satisfy whatever has been said in the passage.  My job is to find a NECESSARY assumption that must-be-true for the passsage (stimulus) to hold.

Nonetheless, the surposed logic which is used in the passage (stimulus) is that the 33% number is a true reflection of those drivers who are speeding on a regular basis.  In other words, those who were issued a speeding ticket were not due to bad luck but due to their normal behavior. Choice B) is necessary for the above logic to hold.

yiayia

楼主为解释公式而加的assumption：超速车=被ticket车，是没有事实根据的。

如果楼主对3%和33%还纠结的话，我可以给一个解释：
撇开regularly, if drivers who equip their vehicles with radar detecters are not more likely to exceed the speed limit  than are drivers who do not, then it should not be  that33% percent of all vehicles ticketed for exceeding the speed limit were equipped with them.
在不考虑其他因素的情况下，如果装雷达探测器的车主不是更可能比那些没装的人超速(换句话说，就是装雷达对是否超速无影响或者甚至会降低超速)，那么装探测器超速人的比例应该不是33%左右（肯定远远小于33%）。因此原推论成立
注意我的逻辑推理顺序：
A=it should be 33 percent of all vehicles ticketed for exceeding the speed limit were equipped with them.
B=drivers who equip their vehicles with radar detecters are more likely to exceed the speed limit  than are drivers who do not.
如果if not B, then not A 成立
那么if  A,then B 成立。

事实上，装雷达探测器的超速驾驶人能更好地规避被ticket的风险，因为他们能发现雷达！所有实际 装雷达测速器超速的人超速的可能性比数据表现的更高。

pirate舟

sdcar2010,谢谢你的解释，同意。然后我又有没想通的地方的，再次请教，在你13楼的推理中： for those drivers who have radar detectors and who got a speeding ticket, they are NOT more likely to exceed the speed limit regularly than are drivers who are not ticketed. This is in contrary to the conclusion of the stimulus -- Drivers who equip their vehicles with radar detectors ARE more likely to exceed the speed limit regularly than are driver who do not.


我觉得前半部分的结论是没有一定contrary to 后面这部分的。因为在这里， drivers who are not ticketed 里面，有的装了radar、有的没装，那么我们依然没有充足的理由来比较装radar和没装radar 谁更可能超速，也就是说这里可能contrary to 也可能没有。

pirate舟

yiayia你好
撇开regularly, if drivers who equip their vehicles with radar detecters are not more likely to exceed the speed limit  than are drivers who do not, then it should not be  that33% percent of all vehicles ticketed for exceeding the speed limit were equipped with them.
在不考虑其他因素的情况下，如果装雷达探测器的车主不是更可能比那些没装的人超速(换句话说，就是装雷达对是否超速无影响或者甚至会降低超速)，那么装探测器超速人的比例应该不是33%左右（肯定远远小于33%）。

你这里就说不通呀。  1、首先结论中是，被ticket同时装雷达的，占被ticket车的33%，你这里就没有考虑到  被ticket车 和 超速车 的区别了。
2、再者，如果我们忽略区别，或者被 ticket的车 有代表性，根据你说的 “(换句话说，就是装雷达对是否超速无影响或者甚至会降低超速)”，那么在被ticket车里面，装雷达的只用等于或小于50%就可以了

sdcar2010

If A=A1 + A2, B = B1 + B2; and A is not more likely to do somethi1ng than B; Then A1 is not more likely to do something than B2.  Same logic!

pirate舟

for those drivers who have radar detectors and who got a speeding ticket, they are NOT more likely to exceed the speed limit regularly than are drivers who are not ticketed. This is in contrary to the conclusion of the stimulus -- Drivers who equip their vehicles with radar detectors ARE more likely to exceed the speed limit regularly than are driver who do not.


麻烦在上述这个推理之中对应一下A1，A2，B1，B2各自所指啊。。我对不上啊~~~If A=A1 + A2, B = B1 + B2; and A is not more likely to do somethi1ng than B; Then A1 is not more likely to do something than B2.
按照这个推论，A是指（装radar+被ticket），B是指 （没被ticket的所有） ，A1指（装radar所有），B2指（没有radar所有）