Question
A drug testing company advertises a test for steroids that is 93.5% effective at detecting steroid use. It has a true negative effectiveness of 93.5%. Suppose 8% of 10,000 professional cyclists are believed to be using steroids.
Suppose the haplessly named Lance Robustcalve tests positive for steroid use. What is the probability that he's really not using steroids?
Suppose the haplessly named Lance Robustcalve tests positive for steroid use. What is the probability that he's really not using steroids?
Answers
henry2,
p = 100% - 8% = 92% = 0.92 = 92/100 = 23/25.
PsyDAG
It doesn't matter how many others are using. You just want the probability that his test is false positive.
p = 100% - 93.5% = ?
p = 100% - 93.5% = ?