Monday Puzzle

The Presurfer, in cooperation with pzzlr.com, brings you a puzzle every Monday. Just to tickle your brain.

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Suppose that you get a strange rash on your arm and you are quite concerned that you might have some rare disease - one that occurs randomly in the general population in only 1 in every 10,000 people. You decide to get tested, and the test comes back positive. To your dismay, the doctor tells you that the test is very accurate, being correct 99% of the time, regardless of whether the result is positive or negative.

What are your chances that you actually have the disease? Is it approximately:

1. 99%
2. 90%
3. 10%
4. 1%

You can find the answer here.