天山 4-35

reohuang

i think the "test accurate" should including the following 2 situations:

a) had the infection and tested positive

b) did not have infection and tested negative

therefore,

accouring to A) we can know 1/8 of tested positive is accurate, and 7/8 of tested positive is inaccurate

according to B) we can know 90% are tested negative and 10% are tested positive

according to A)+B) we can only know the situation a)=10%*1/8, still do not know the situation b)

therefore the condition A) and B) are not sufficient , and the answer should be E

bobochen

请问charmant: 你的式子中90%nx%应该是呈阴性吧！不知我的理解正确否？

WalkByFaith

to 小豆包:

请帮我看看:

11 楼的,

i think the "test accurate" should including the following 2 situations:

a) had the infection and tested positive

b) did not have infection and tested negative

therefore,

accouring to A) we can know 1/8 of tested positive is accurate, and 7/8 of tested positive is inaccurate

accouring to A) we can know 7/8 of tested positive is accurate, and 1/8 of tested positive is inaccurate吧!

according to B) we can know 90% are tested negative and 10% are tested positive

according to A)+B) we can only know the situation a)=10%*1/8, still do not know the situation b)

应该是 according to A)+B) we can only know the situation a)=10%*7/8, still do not know the situation b)

therefore the condition A) and B) are not sufficient , and the answer should be E

catorina

哎...没太明白，若是这种思路，岂不是很多题目都不能认定给出的条件的正确性了？晕

but thanks you guys anyway.

wenmei

我觉得简单的理解就是：

如果检测出来是positive的不一定infenction，那么同理检测出来是negative的也有可能是infection的.

条件只给出了检测出来是negative的比例，没有给出检测出来是negative但事实上是infection的比例，因此答案为E。

juliet01192000

先不说是否看懂上面讨论的解法：我的问题：

1 检测出来是positive的不一定infenction，那么同理检测出来是negative的也有可能是infection的.

上面这种假设，只能从（1）中看出来，当考虑（2）是否正确时，可否抛弃（1）给的情况，在没有误诊的情况下考虑。

2 不明白中文意思：检测出来是positive的不一定infenction，那么同理检测出来是negative的也有可能是infection的.

盼解答！谢谢！：）

juliet01192000

up!

juliet01192000

自己顶，直到nn来，nn快出现吧，芝麻开门。。。：）

juliet01192000

虽然最后nn还是没出现，但是还好，自己终于想明白了！：）

mayce

以下是引用charmant在2005-1-26 13:47:00的发言：

(1)检验出来阳性的有1/8健康(误诊率为1/8）

(2)90%的测验成阴性

为什么误诊率为1/8？