use the Wilcoxon rank-sum test. Taxi-Out Times ?Listed below are samples of taxi-out times (min) for American Airlines Flights 19 and 21 (from Data Set 15 in Appendix B). Use the sample data to test the claim that taxi-out times for Flight 19 and Flight 21 have the same median. Use a 0.05 significance level. Flight 19 15 12 19 18 21 20 13 15 43 18 17 19 Flight 21 13 20 12 17 35 19 22 43 49 45 13 23

Solution 6BSC Step 1 : Given, In the above example the data consists of the taxi-out times of American Airlines Flights 19 and 21 taken randomly, so the observations from the same population. Hence first requirement of the Wilcoxon Rank-Sum test satisfied. Each samples contains 12 values in each taxi-out times, it satisfies the second condition that the each sample should have the same median. Therefore, both the requirements of the Wilcoxon Sum-Rank test satisfies. Hypothesis : H :0The median of the taxi-out times of flight 19 is equal to the median of the taxi-out times of flight 21. H :1The median of the taxi-out times of flight 19 is not equal to the median of the taxi-out times of flight 21. Step 2 : We have 24 observations from Flight 19 and 21. Based on the values we give ranks, if it is least value is 12 which appears twice so its rank is equal to the mean of 1 and 2, i.e, 1.5. If there is a tie then mean of the values is the rank, for example the rank of 5 is 2.5. Highest value is 49 which is assigned the rank 24. Ranks for the taxi-out times of flight 19 are 6.5, 1.5, 13, 10.5, 17, 15.5, 4, 6.5, 21.5, 10.5, 8.5, 13. The sum of the ranks for taxi-out times of flight 19 = 128.