10.22 Do upload and download speeds vary between cities and Internet service providers? The file [Internet Provider Speeds] contains the upload and download speeds in Mbps in 40 different cities for four Internet service providers, AT&T, T-Mobile, Sprint, and Verizon, as measured in November 2017. In this problem, you have decided to focus on the difference in the download times between AT&T and Verizon. Source: Data extracted from "Speedsmart Wireless Speed Index," bit.ly/2Fjordt. City AT&T Upload Speed AT&T Download T-Mobile Upload T-Mobile Download Sprint Upload Sprint Download Verizon Upload Speed Speed Speed Speed Speed Speed Verizon Download Speed Albuquerque NM 19.07 6.06 17.94 14.97 11.98 5.17 18.51 9.87 Atlanta GA 23.15 6.97 37.50 8.79 32.71 2.79 36.98 11.90 Baltimore MD 28.22 6.83 21.37 6.84 24.45 2.73 41.27 9.54 Birmingham AL 20.97 5.79 32.28 8.95 15.01 2.78 41.05 10.96 Boston MA 23.96 8.85 22.76 11.41 28.14 3.31 45.20 13.36 Buffalo NY 8.10 5.82 26.65 3.25 24.45 5.49 20.74 4.76 Charlotte NC 27.19 8.10 26.39 9.71 16.47 1.98 22.03 7.89 Chicago IL 31.37 8.31 25.59 9.90 24.77 4.89 33.04 11.86 Cincinnati OH 16.97 5.43 34.68 4.86 15.21 3.37 33.73 6.67 Cleveland OH 26.81 8.80 12.85 5.37 18.42 4.03 23.57 8.33 Dallas TX 17.02 8.17 32.04 10.75 18.57 2.33 39.89 14.23 Denver CO 25.36 5.49 26.64 6.52 11.87 5.35 21.37 6.44 Detroit MI 25.39 6.91 37.14 10.35 15.87 3.25 36.99 12.87 Hartford CT 20.91 6.53 21.43 5.56 24.46 8.19 32.46 6.21 Houston TX 24.11 8.01 27.46 9.52 22.60 2.70 19.45 6.36 Indianapolis IN 26.14 10.79 10.71 7.46 24.46 3.09 29.95 3.54 Jacksonville FL 15.88 5.70 55.51 20.56 17.34 3.20 26.42 4.98 Kansas City MO 31.49 6.00 39.83 6.07 18.88 4.09 30.43 8.00 Las Vegas NV 22.80 8.62 18.69 9.50 14.58 2.46 18.19 4.94 Little Rock AK 16.72 5.36 14.21 4.92 12.49 7.02 27.19 9.38 Los Angeles CA 25.14 8.50 21.57 10.00 27.16 3.47 28.63 11.13 Miami FL 20.84 5.99 43.60 11.20 26.42 2.38 27.91 9.08 Milwaukee WI 29.89 7.00 15.96 8.74 16.40 1.74 42.09 12.07 Minneapolis MN 28.50 7.33 34.57 11.11 19.44 4.01 42.56 13.09 a. At the 0.05 level of significance, is there evidence of a difference in the mean download speed between AT&T and Verizon? b. What assumption is necessary to perform this test? c. Use a graphical method to evaluate the assumption made in (a). d. Construct and interpret a 95% confidence interval estimate of the difference in the mean download speed between AT&T and Verizon.