Question 271871
Use the normal distribution to approximate the desired probability. International Airlines reports that 74% of its planes are on time. 
A check of 60 randomly selected planes shows that 38 of them arrived on time. Find the probability that among the 60 planes, 38 or fewer arrive on time.
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If p = 0.74, the mean for all samples of size 60 is np = 60*0.74 = 44.4
and the standard deviation is sqrt(npq) = sqrt(60*0.74*0.26) = 3.3976
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Then z(38) = (38-44.4)/3.3976 = -1.8837

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P(x<=38) = P(z< -1.8837) = 0.0298
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Cheers,
Stan H.