Wrong!

The 95% is the accuracy of the test, in other words, the probaility to test positive if you have the disease. However, you need to compute the probability that you have the disease if you test positive and in order to do so, you need to consider not only the accuracy of the test, but also the fact that the disease is rare.

It is a common mistake to confuse the probability to test positive given that you have the disease with the probability to have the disease given that you test positive. In fact, a study done at Harvard Medical School showed that 30 out of 60 doctors who were presented this problem gave the wrong answer 95%!

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