Question 268712
A major airline company is concerned that its proportion of late arrivals has increased from the historical level of 18%. 
The test the hypothesis, 
Ho: pie<= 0.18 
vs H1: pie>.18 
The airline takes a random sample of 1240 flights and finds 310 arrived late.
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sample proportion = phat = 310/1240 = 0.25
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What is the test statistic?
ts = z(0.25) = (0.25-0.18)/sqrt(0.18*0.82/1240) = 0.07/0.0109 = 6.4160
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Cheers,
Stan H.