求助CR一题！There is a great deal of geographical ...

apple0000006

There is a great deal of geographical variation in the frequency of many surgical procedures—up to tenfold variation per hundred thousand people among different areas in the numbers of hysterectomies, prostatectomies, and tonsillectomies．
To support a conclusion that much of the variation is due to unnecessary surgical procedures，it would be most important to establish which of the following?
(A) A local board of review at each hospital examines the records of every operation to determine whether the surgical procedure was necessary．
(B) The variation is unrelated to factors (other than the surgical procedures themselves) that influence the incidence of diseases for which surgery might be considered．
(C) There are several categories of surgical procedure(other than hysterectomies， prostatectomies，and tonsillectomies)that are often performed unnecessarily．
(D) For certain surgical procedures．it is difficult to determine after the operation whether the procedures were necessary or whether alternative treatment would have succeeded．
(E) With respect to how often they are performed unnecessarily, hysterectomies，prostatectomies，and tonsillectomies are representative of surgical procedures in general

[此贴子已经被作者于2008-6-1 11:55:36编辑过]

jetking

关键是题意的理解：

原文的意思大致：在不同地区，做这些XXX疾病的外科手术的数量之间差距每几十万人几十倍。哪么，下列那个支持一个结论（这些外科手术的数量上的差异是由于不必要的手术流程造成，而不是其他因素造成的）。

哪么，B说：这些差异是与那些可以导致疾病并且考虑进行外科手术的因素无关。

直接说出了原因。

[此贴子已经被作者于2008-6-1 13:58:51编辑过]

f0070515

This is from the OG 10 edition.

This is a special type of the strengthen question where the conclusion is in the question stem. Please be on the lookout for this as it occurs fairly regularly.

The conclusion is "much of the variation is due to unnecessary surgical procedures" This indicates a cause and effect relationship. We are, in effect, saying that the reason that there is a geographical variation in the listed procedures is because in the areas where more procedures are performed many of those procedures are not necessary.

Now there could be other reasons for a variation in the number of surgeries. For example, the new natural gas wells that are being drilled in people's back yards have been proven to contaminate the water supply and so it would be very reasonable to see additional cases of cancer and therefore additional procedures near these poisonous wells. So that would be another cause not unnecessary procedures, but variations in the toxicity of various places around the U.S. (or the world depending on how you read the question).

In order to strengthen a question that involves cause and effect, you will want to consider the possibility of blocking an alternate cause. In this case we are saying the cause is the "unnecessary procedures" so we want to block the things that would make these procedures necessary - like variations in the age of the population, the health of the people, the quality of the water, even the ability of the people to pay for the procedures.

Answer Choice B does this. It says, "The variation is unrelated to factors (other than the surgical procedures themselves) that influence the incidence of diseases for which surgery might be considered." So this blocks the idea that the cause of varying rates of procedures would be any of the factors (age, health, toxins) etc. mentioned above. So we strengthen one cause by blocking another.
来自 http://www.beatthegmat.com/geographic-variation-t46931.html#343608

newconcept123

我尝试来解释一下：
geographical variation 简称 GV
surgical procedure 简称 SP

Premise: much GV in SP
Conclusion: unnecessary SP ---> much GV

选项B是双重否定，很难读懂的。
可以从其他角度来考虑：
（strenthen题型）根据CR Bible 的解题法来，assumption 要么排除其他因数
(Eliminate any  alternate causes for the stated effect)
要么加强 premise
选项Ｂ做到了前者。
还有就是其他四个选项比较容易排出，在读不懂选项Ｂ的情况，也可以用排除法。

A weaken
C irrelevant
D irrelevant
E irrelevant

vikiyao

楼上的牛人啊~~~