A bit off-topic:
Because AIDS and pregnancies are such rare cases after condom use, the "98% effective" label on AIDS/pregnancy tests can be misleading.
If one tests positive on either of these tests, there is not a 2% chance that one is actually positive. Because there are SO many more false-positives than actual pregnancies or AIDS cases, the chances of a false-positive are actually very high. (I don't remember the correct number, but it may have been something like 70% of all positives are false.)
Don't ask me to explain my math, my teacher did it in class and I didn't take notes.
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