In tests for Feline Leukemia Virus (FeLV), a serious disease of domestic cats, a false positive result indicates that a cat has FeLV, when in fact, it does not; a false negative result indicates that a cat does not have FeLV when, in fact, it does. To detect FeLV most accurately, veterinarians should use the laboratory test that has the lowest proportion of false negative results.

Which of the following, if true, gives the most support to the recommendation above?

E- All laboratory tests to detect FeLV have the same rate of false positive results.

This one is simply a matter of there being 2 tests. Event Neg and Event Pos. So in the case of E is is saying that NO MATTER WHAT all laboratory tests to detect FeLV will have the same rate of false positive. Which means that you're going to want to pick the lab test that has the lowest proportion of negative results and therefore it supports the theory. so E is the correct answer.

To make it easier to understand, you obviously want the least number of errors so lets take 5 random tests:
-------------Pos Errors----Neg Errors-------Total Errors
Lab test 1-------3-------------2----------------5
Lab test 2-------3-------------3----------------6
Lab test 3-------3-------------4----------------7
Lab test 4-------3-------------1----------------4
Lab test 5-------3-------------2----------------5

Therefore it doesnt matter what the proportion of Pos errors is, the total number of errors goes down. And for the record with False Pos it tells them that they have FeLV when they don't so they would have to take the test again to confirm because it would be costly for treatment just as they would take the False Neg again to make sure the cat is ok. Either way they would take the test to confirm a second time there is no difference between two false.
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+1 for E

Good explanations i kudos but im on a mobile phone

Posted from my mobile device

Choice E is the correct one.
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