OG-172

wendybao

172. There is a great deal of geographical variation in the frequency of many surgical procedures—up to tenfold variation per hundred thousand between 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, B prostatectomies, and tonsillectomies are representative of surgical procedures in general.

172.

To establish that much of the variation is due to unnecessary surgical procedures, it is necessary to eliminate the possibility that the geographical variation reflects variation in the incidence of disease treated with these procedures. Choice B, if established, would eliminate this possibility and is thus the best answer.

Review boards (choice A) would provide some control against unnecessary procedures, so choice A would, if anything, tell against the suggested conclusion. Neither choice C nor choice E bears on the conclusion, since neither the conclusion nor the cited geographical variation involves procedures are of the kind choice D describes, the difficulty of determining an individual operation’s necessity would merely increase the difficulty of verifying the suggested conclusion.

看了曾经有过的讨论和OG的解释，还不是太明白，麻烦NN解释一下。Many thanks!

sensornet

俺不是NN。我也正看这道题，OG给的解释确实比较笼统。你哪里不明白，请说得清楚一些。这样大家好一起讨论。

另，我跟了一个关于E为什么不对的帖子。请指点。http://forum.chasedream.com/dispbbs.asp?BoardID=24&ID=8281