Fifteen sets of identical twins were enrolled in a study to measure the effect of air pollution on neonatal mortality. One twin in each set was randomly assigned to the intervention group (renewable energy) or control group (non-renewable energy). At the end of the day, the Air Quality Index (AQI) was recorded. as shown in the data below. Subject id AQI 1 AQI 2 1 65 83 2 67 75 3 75 72 4 77 76 5 69 78 6 65 30 7 73 72 8 78 31 9 70 7O 10 72 78 11 73 77 12 79 71 13 68 37 14 73 7O 15 71 75 a) Perform a distribution-free test on these data and write a summary of what the result show b) State briefly why you think a distribution-free test was chosen to analyse these data