12. Two fuel additives are tested to determine their effect on miles per gallon for passenger cars. Test results for 12 cars follow; each car was tested with both fuel additives. Use a = .05 and the Wilcoxon signed-rank test to see whether there is a significant difference between the median miles per gallon for the additives. Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-200-203 18.2 Wilcoxon Signed-Rank Test 887 Additive Additive Car 2 Car 1 2 file 1 20.12 18.05 7 16.16 17.20 23.56 21.77 8 18.55 14.98 tive 22.03 22.57 9 21.87 20.03 4 19.15 21.23 17.06 10 24.23 21.15 21.22 11 23.21 22.78 6. 24.77 23.80 12 25.02 23.70