SOLUTION: Smokers: According to the American Lung Association, 90% of adult smokers started smoking before turning 21 years old. Ten smokers 21 years old or older are randomly selected, and

Question 935483: Smokers: According to the American Lung Association, 90% of adult smokers started smoking before turning 21 years old. Ten smokers 21 years old or older are randomly selected, and the number of smokers who started smoking before 21 is recorded.
Explain why this is a binomial experiment
Find and interpret the probability that exactly 8 of them started smoking before 21 years of age.
Find and interpret the probability that fewer than 8 of them started smoking before 21 years of age.
Find and interpret the probability that between 7 and 9 of them, inclusive, started smoking before 21 years of age
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
90% of adult smokers started smoking before turning 21 years old. Ten smokers 21 years old or older are randomly selected, and the number of smokers who started smoking before 21 is recorded.
Explain why this is a binomial experiment
two possibilities:: yes or no ; p = 0.9 for each individual ; independent events
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Find and interpret the probability that exactly 8 of them started smoking before 21 years of age.
P(x = 8) = 10C8*0.9^8*0.1*2 = binompdf(10,0.9,8) = 0.1937
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Find and interpret the probability that fewer than 8 of them started smoking before 21 years of age.
P(0<= x <=7) = binomcdf(10,0.9,7) = 0.0702
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Find and interpret the probability that between 7 and 9 of them, inclusive, started smoking before 21 years of age
P(7<= x <=9) = binomcdf(10,0.9,9)-binomcdf(10,0.9,6) = 0.6385
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Cheers,
Stan H.
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