Question

The Department of Defense tests two types of aircraft, type A and type B, to determine whether their mean speed under a particular set of conditions is same or not. In four tests of type A aircraft the mean speed under the prescribed conditions was 590 mph, and the standard deviation was 100 mph. In four tests of type B aircraft the mean speed under these conditions was 750 mph, and the standard deviation was 90 mph. The Defense Department wants to detect differences in mean speed, regardless of which type of aircraft may be faster. Assume that the speeds of each type of aircraft are normally distributed.

A. Find a 90% confidence interval for the difference of mean speeds. Write a sentence interpreting the confidence interval.

B. Could there be enough evidence, at α = 0.02, that the mean speeds differ for these two types of aircraft? Write down the H0, Ha, test statistic, rejection region.

Answer 1