Question 177903: In 1992, the FAA conducted 86,991 pre-employment drug tests on job applicants who were to be engaged in safety and security related jobs, and found that 1,143 were positive.
(a) Construct a 95 percent confidence interval for the population proportion of positive drug tests.
(b) Why is the normality assumption not a problem, despite the very mall value of p?
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! In 1992, the FAA conducted 86,991 pre-employment drug tests on job applicants who were to be engaged in safety and security related jobs, and found that 1,143 were positive.
(a) Construct a 95 percent confidence interval for the population proportion of positive drug tests.
p-hat = 1143/86991 = 0.01314
E = z = 1.96[sqrt(0.01314*0.98686)/86991] = 0.0254
95% CI: 0.01314-0.0254 < p < 0.01314 +0.0254
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(b) Why is the normality assumption not a problem, despite the very mall value of p?
The sample is large so np > 5 and nq > 5
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Cheers,
Stan H.
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