The Bureau of Transportation Statistics provides data on U.S. airline flights. T

Question

The Bureau of Transportation Statistics provides data on U.S. airline flights. The airborne times (in minutes) for United Airlines flight 448 from Albuquerque to Denver on 10 randomly selected days between January 1, 2003, and March 31, 2003, are in the following table. (a) Compute a 90% confidence interval for the mean airborne time for flight 448. (Use Table 3 in Appendix A. Give the answer to two decimal places.) (b) Give an interpretation of the 90% confidence level associated with the interval estimate in Part (a). It's 90% probability that the airborne time for flight 448 is in this interval. If we obtain other samples, 90% of them would contain the true population mean. If the same sampling method was used to obtain other samples of the same size and confidence intervals were calculated from these samples, 90% of them would contain the true population mean.

Explanation / Answer

From the given data we can calculate the mean and std. dev. of sample

mean = 54.2
std. dev. = 3.6758
t-value for 90% CI for 9 degrees of freedom = 1.833

Standard Error = std.dev. / sqrt(n) = 3.6758/sqrt(10) = 1.1624

Margin of error = t*SE = 1.833 * 1.1624 = 2.131

Confidence Interval = (mean +/- ME) = (54.2 - 2.131, 54.2 + 2.131) = (52.069, 56.331)

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