Your doctor screened you for a particular virus and the results came back positive, indicating that you have the virus. How concerned should you be?
What if your doctor said:
* The test is 100 percent accurate in indicating a person has the virus when they actually have it.
* The test indicates a person has the virus when they don't actually have it 5 percent of the time.
* The virus is present in one out of five hundred people.
What's the probability (percentage) that you actually have the virus?
2007-08-24 10:20:43 · 6 answers · asked by Anonymous in Science & Mathematics ➔ Other - Science
Much of what you posted is irrelevant to the problem. If the virus is present in 1/500 people, then the probability that you have it is:
1/500 x 100% = 0.2%
I'd also like to note to the people who seem to be having trouble following the irrelevant data. He says that the test is accurate 100% of the time in people who have the virus. The 5% are false positives.
So let's say that there is 200 people. 100 have the virus, 105 test positive. All 100 who have the virus tested positive, but 5% of people who do not have the virus also tested positive. This would have no bearing on your chances of having the virus if it's known to be present in 1/500 people. The information simply describes the level of accuracy of the test, not the proportion of people with the virus.
2007-08-24 10:38:16 · answer #1 · answered by Anonymous · 1⤊ 0⤋
95%. The test is wrong only 5% of the time, when you have a false symtom/symptoms.
Regardless of how many actually have the virus the day you tested positive, the test is all that matters now.
2007-08-24 18:44:18 · answer #2 · answered by Your Uncle Dodge! 7 · 0⤊ 1⤋
95%
there are no false negtives
since there is a 5% chance of false positive
you have a 95% chance of having the virus
since you came back positive who cares what percentage of the population has the virus
2007-08-24 17:40:56 · answer #3 · answered by Mark W 2 · 1⤊ 2⤋
your first premise contradicts your second premise.
your first premise basically stated that if the machine said you have the virus, then you have the virus.
your second one said that the machine can make mistakes, which implies that there is a chance that the machine is wrong.
these two contradict, you see. you cant have the virus but not have the virus at the same time
2007-08-24 18:21:35 · answer #4 · answered by Anonymous · 1⤊ 2⤋
im not sure im right but im guessing its 1% so u wouldnt be that concerned. :) luv these kinds of problems! ~xoxo
2007-08-24 17:28:00 · answer #5 · answered by Erin Elaine. 3 · 0⤊ 0⤋
Hmmmmmmmmm
95%
i dont know!
2007-08-24 19:09:27 · answer #6 · answered by Anonymous · 0⤊ 0⤋