E = the event that an anabolic steroid detection test gives a positive result
F = the event that the athlete uses steroids.

We are given P(E | F), the probability that the test is positive for an athlete who uses steroids = 0.95. But this tells us nothing about P(F | E), the probability that an athlete uses steroids given that the test is positive.

P(F | E) could be any number between 0 and 1. For instance, if no-one on the team was using steroids, the P(F | E) = 0, and the positive result must be a false positive. On the other hand, if the whole team had been using steroids, then P(F | E) = 1.

Therefore, we need more information to answer this question.


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