Survival times of rats

Abstract

Table S.3 (J.S. Maritz, personal communication) gives data from an experiment on carcinogenesis in rats. Eighty rats were divided at random into 4 groups of 20 rats each, and treated as follows:

Group I D,no I,no P;

II D, I,noP;

III D,no I, P;

IV D, I, P;

where D is thought to produce cancer, I is thought to act as an inhibitor and P is thought to accelerate the appearance of cancer. The data in Table S.3 are survival times in days; after 192 days the experiment was ended, and a post mortem was conducted on every surviving rat to assess the presence or absence of cancer. In the table, 192^- means that the rat survived 192 days but was found to have cancer. The superscript ⁺ means death from a cause unrelated to cancer; in particular, 192⁺ means that on post mortem the rat did not have cancer.