Refer to Exercise 11-18.

(a) Is there a difference in the mean number of passengers bumped using software packages 1 and 2 from that using software packages 3 and 4? Test at the 10%

level of significance.

(b) Find a 95% confidence interval for the contrast that tests for the difference in the mean number of passengers bumped using software package 3 and the average of that using software packages 1 and 2.