There is nothing vague

here.
A test result is accurate if the result equals to the truth. Consider the pair of random variables: (X, Y),
X is the true status of the patients, can be either + (HIV) or - (non HIV).
Y is the test result of the patient from the hospital, + (test says HIV +) or - (test says HIV -).
There 4 possible non-overlapping results of the test:
(+, +), (-, -), (+, -) or (-, +).
The first two cases are accurate (i.e., X=Y), the last two cases are failures. The accuracy of the test is defined as P(X=Y) or statistically, #of (++) and (--) over the total # of samples.

所有跟帖： 

• 别给别人上课来显示你的“聪明” -那叫哗众取宠- ♀ (0 bytes) () 07/14/2004 postreply 16:22:41

• LoL.. I am idiot :D -idiot94- ♀ (0 bytes) () 07/14/2004 postreply 16:48:28

• He is not“聪明”, but -sentinel- ♀ (99 bytes) () 07/14/2004 postreply 17:17:46

• 你是轮子派来的不？请跟我去兵坛，让我好好操操你 -花剪刀- ♀ (0 bytes) () 07/14/2004 postreply 17:44:26

• Blind guy, get out here! -sentinel- ♀ (0 bytes) () 07/14/2004 postreply 17:48:37

• 回复：There is nothing vague -heg- ♀ (527 bytes) () 07/14/2004 postreply 17:49:52