A carcinogenicity study was conducted to examine the tumor potential of a drug product scheduled for initial testing in humans. A total of 300 rats (150 males and 150 females) was studied for a 6- month period. At the beginning of the study, 100 rats (50 males, 50 females) were randomly assigned to the control group, 100 (50 males, 50 females) to the low- dose group, and the remaining 100 (50 males, 50 females) to the high- dose group. On each day of the 6- month period, the rats in the control group received an injection of an inert solution, whereas those in the drug groups received an injection of the solution plus drug. The sample data are shown in the accompanying table.

a. Conduct a test of whether there is a significant difference in the proportions of rats having one or more tumors for the three treatment groups with a = .05.
b. Does there appear to be a drug- related problem regarding tumors for this drug product? That is, as the dose is increased, does there appear to be an increase in the proportion of rats with tumors?

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Number of Tumors Rat Group One or More None Control 10 90 Low dose 14 86 High dose 19 81