Question 272169
The rates of on-time flights for commercial jets are continuously tracked by the U.S. Department of Transportation. Recently, Southwest Air had the best reate with 80 % of its flights arriving on time. A test is conducted by randomly selecting 20 Southwest flights and observing whether they arrive on time. 
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Binomial Problem with n = 20 ; p = 0.8
(a) Find the probability that at least 18 flights arrive on time. 
P(18<= x <=20) = 1-binomcdf(20,0.8,17) = 0.2061
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Cheers,
Stan H.