24. A certain airport security scanner designed to detect explosives in luggage will alert the scanner’s operator whenever the piece of luggage passing under the scanner contains an explosive. The scanner will erroneously alert the operator for only one percent of the pieces of luggage that contain no explosives. Thus in ninety-nine out of a hundred alerts explosives will actually be present.
The reasoning in the argument is flawed because the argument
(A) ignores the possibility of the scanner’s failing to signal an alert when the luggage does contain an explosive (B) draws a general conclusion about reliability on the basis of a sample that is likely to be biased (C) ignores the possibility of human error on the part of the scanner’s operator once the scanner has alerted him or her (D) fails to acknowledge the possibility that the scanner will not be equally sensitive to all kinds of explosives (E) substitutes one group for a different group in the statement of a percentagey
结论：无论什么时候都可以detect！第一句：A certain airport security scanner designed to detect explosives in luggage will alert the scanner’s operator whenever the piece of luggage passing under the scanner contains an explosive.
cause : The scanner will erroneously alert the operator for only one percent of the pieces of luggage that contain no explosives. (scanner 有１％的错误率：会将没有炸药的认为有）
conclusion: in ninety-nine out of a hundred alerts explosives will actually be present. （１００次警示中９９中会有炸药）
但是，１％的概率并不表示是刚好１００件里有一件，可能１０００件里有１０件，而这１０件可能一起出现在前１００件中，这样不就在１００件中有１０件误警． E 选项说明了这个问题，所以对
E ) substitutes one group for a different group in the statement of a percentagey
京公网安备11010202008513号 京ICP证101109号 京ICP备12012021号
发表于 2005-7-1 06:58:00
楼主