A problem with a telephone line that prevents a customer from receiving or making calls is upsetting to both the customer and the telephone company. The file Phone contains samples of 20 problems reported to two different offices of a telephone company and the time to clear these problems (in minutes) from the customers' lines:
Central office | Time to Clear Problems (Minutes)

Central office | Time to Clear Problems (Minutes)

a. Is there evidence of a difference in the median time to clear problems between offices? (Use α = 0.05.)
b. What assumptions must you make in (a)?

148 1.75 0.78 2.85 0.52 1.60 4.15 3.97 1.48 3.10 1.02 0.53 0.93 1.60 0.80 1.05 6.32 3.93 5.45 0.97 7.55 3.75 0.10 1.10 0.60 0.52 3.30 2.10 0.58 4.02 3.75 0.65 1.92 0.60 153 4.23 0.08 1.48 1.65 0.72