1) A lottery game has thefollowing rules: pick 6 distinct numbers from a set of4
ID: 2954814 • Letter: 1
Question
1) A lottery game has thefollowing rules: pick 6 distinct numbers from a set of49.
The grand prize winner picks 6numbers out of 6 correctly.
(i) What is the probability ofwinning the grand prize?
Manyprofessional sports leagues test their players for steroids. Manyplayers
that testpositive for steroid use claim that their test is a ‘falsepositive,” that is,
the test cameup positive for steroid use when the player has not actuallyused
steroids.Suppose that an anonymous survey reveals that 30% of all playersin
the leaguetake steroids. The company that designs the drug test claims thatthe
testcorrectly identifies drug use (as well as non-use) 99% of the time.Find the
probabilitythat the test incorrectly identifies a steroid user when the playerhas
truly never usedsteroids.
Explanation / Answer
1) A lottery game has thefollowing rules: pick 6 distinct numbers from a set of49.
The grand prize winner picks 6numbers out of 6 correctly.
(i) What is the probability ofwinning the grand prize?
choose 6 winning numbers=6*5*4*3*2*1=
choose 6 number from 49 =49*48*47*46*45*44=6.08281864*1062
Probability ofwinning 720/6.08281864*1062=1.18366179*10-60
Manyprofessional sports leagues test their players for steroids. Manyplayers
that testpositive for steroid use claim that their test is a ‘falsepositive,” that is,
the test cameup positive for steroid use when the player has not actuallyused
steroids.Suppose that an anonymous survey reveals that 30% of all playersin
the leaguetake steroids. The company that designs the drug test claims thatthe
testcorrectly identifies drug use (as well as non-use) 99% of the time.Find the
probabilitythat the test incorrectly identifies a steroid user when the playerhas
truly never usedsteroids.
p(of not a steroiduser)=.70
P(of testwrong)=.01
these areindependent
P(of not a steroid userand test wrong)= .7(.01)=.007
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