In the airline business, "on-time" flight arrival is important for connecting flights and general customer satisfaction. Is there a difference between summer and winter average on-time flight arrivals? Let x1 be a random variable that represents percentage of on-time arrivals at major airports in the summer. Let x2 be a random variable that represents percentage of on-time arrivals at major airports in the winter. A random sample of n1 = 16 major airports showed that x1 = 74.9%, with s1 = 5.3%. A random sample of n2 = 18 major airports showed that x2 = 70.2%, with s2 = 8.6%.
Note: For degrees of freedom d. f. not in the Student's t table, use the closest d. f. that is smaller. In some situations, this choice of d. f. may increase the P-value a small amount and thereby produce a slightly more "conservative" answer.
(a) Does this information indicate a difference (either way) in the population mean percentage of on-time arrivals for summer compared to winter? Use
α = 0.05.
What is the level of significance?
What is the value of the sample test statistic? (Round your answer to three decimal places.)
(b) Find a 95% confidence interval for
μ1 − μ2.
(Round your answers to two decimal places.)
lower limit %
upper limit