Cancer treatment by means of chemicals-chemotherapy-kills both cancerous and normal cells. In some instances, the toxicity of the cancer drug-that is, its effect on normal cells-can be reduced by the simultaneous injection of a second drug. A study was conducted to determine whether a particular drug injection reduced the harmful effects of a chemotherapy treatment on the survival time for rats. Two randomly selected groups of 12 rats were used in an experiment in which both groups, call them A and B, received the toxic drug in a dose large enough to cause death, but in addition, group B received the antitoxin, which was to reduce the toxic effect of the chemotherapy on normal cells. The test was terminated at the end of 20 days, or 480 hours. The survival times for the two groups of rats, to the nearest 4 hours, are shown in the table. Do the data provide sufficient evidence to indicate that rats receiving the antitoxin tend to survive longer after chemotherapy than those not receiving the antitoxin? Use the Wilcoxon rank sum test with α =.05.

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Chemotherapy Only Chemotherapy Plus Drug 84 128 168 92 184 92 76 104 72 180 144 120 140 184 368 96 480 188 480 244 440 380 480 196