一道弄晕我的因果关系问题--LSAT-1-4-21

gracehu

21.    A low-pressure weather system is approaching Plainville; rainfall results from about 70 percent of such systems in the Plainville area. Moreover, the current season, spring, is the time of year in which thundershowers, which sometimes result from low-pressure systems, are most likely to occur in Plainville.

Knowing which one of the following, in addition to the information above, would be most useful for determining the probability that Plainville will have a thundershower soon?

(A) the percentage of thundershowers in Plainville that occur in the spring
(B) the percentage of spring rainfalls in Plainville that are thundershowers
(C) the percentage of thundershowers in Plainville that result from low-pressure systems
(D) whether low-pressure systems in other areas are associated with rainfall
(E) whether Plainville has more or fewer thundershowers each spring than do nearby towns


The answer is B! Why not C?
Thx in advance for any explanation

[此贴子已经被作者于2003-11-29 10:23:29编辑过]

gracehu

会不会是因为问题中的'IN ADDITION TO'啊?

browse

注意C并不能推出spring 的 thundershower probability, 它可能是全年的结果。
而由B我们可以从lowpressure * 70%--->rainfall possibility + B中条件(spring rainfalls that are thundershowers)----> the possibility of spring thundershower rainfalls under lowpressure  weather system.

以下是引用gracehu在2003-11-29 10:17:00的发言：
21. A low-pressure weather system is approaching Plainville; rainfall results from about 70 percent of such systems in the Plainville area. Moreover, the current season, spring, is the time of year in which thundershowers, which sometimes result from low-pressure systems, are most likely to occur in Plainville.

Knowing which one of the following, in addition to the information above, would be most useful for determining the probability that Plainville will have a thundershower soon?

(A) the percentage of thundershowers in Plainville that occur in the spring
(B) the percentage of spring rainfalls in Plainville that are thundershowers
(C) the percentage of thundershowers in Plainville that result from low-pressure systems
(D) whether low-pressure systems in other areas are associated with rainfall
(E) whether Plainville has more or fewer thundershowers each spring than do nearby towns


The answer is B! Why not C?
Thx in advance for any explanation

[此贴子已经被作者于2003-11-29 10:23:29编辑过]

Snazzy

Hi, there, i have got the right answer and am trying to give you an explanation, which you might agree with:

Since both rainfall and thundershower result from low-pressure weather system, it's enough to only consider the possibility of thundershower(thunder with rainfall). We already know there is 70 percent of the chance to have rainfall. If we know the percentage of thunder with rainfall, say 40%, it is easy to know the possibility of thurdershower, which is 70% times 40%, 28%. (0-grade Math PS)   Snazzy Nov. 28

21. a low-pressure weather system is approaching plainville; rainfall results from about 70 percent of such systems in the plainville area. moreover, the current season, spring, is the time of year in which thundershowers, which sometimes result from low-pressure systems, are most likely to occur in plainville.

knowing which one of the following, in addition to the information above, would be most useful for determining the probability that plainville will have a thundershower soon?

(a) the percentage of thundershowers in plainville that occur in the spring
(b) the percentage of spring rainfalls in plainville that are thundershowers
(c) the percentage of thundershowers in plainville that result from low-pressure systems
(d) whether low-pressure systems in other areas are associated with rainfall
(e) whether plainville has more or fewer thundershowers each spring than do nearby towns


the answer is b! why not c?
thx in advance for any explanation

mariezhu

这道题讨论过，搜索一下吧！
另外文中已经有thundershower和lowpressure weather system的关系了，
缺的是rainfall和thundershower的关系

gracehu

thx!browse,Snazzy,mareizhu! The explanations are very clear and helpful!

dphxmg

C所要表达的是由low-pressure system 所导致的thundershowers 占到所有thundershowers 的多少。因此，你不可能知道仅由这个比率来预测未来的某个low-pressure system有多大可能带来thundershowers.

the percentage of thundershowers in Plainville that result from low-pressure systems

如果C 被改成the percentage of low-pressure systems in Plainville that result in thundershowers, 那末，它就能成为一个好的选项。

jameswoods

以下是引用dphxmg在2005-3-26 22:28:00的发言：

C所要表达的是由low-pressure system 所导致的thundershowers 占到所有thundershowers 的多少。因此，你不可能知道仅由这个比率来预测未来的某个low-pressure system有多大可能带来thundershowers.

the percentage of thundershowers in Plainville that result from low-pressure systems

如果C 被改成the percentage of low-pressure systems in Plainville that result in thundershowers, 那末，它就能成为一个好的选项。

dphxmg  GG 的回复令人豁然开朗，

顶

beautyup

同意七楼的解释！

C)选项的表述有问题！

quiny

3x