data from Exercise 7.13, p225
rats data frame has 50 rows and 4 columns.
This data frame contains the following columns:
Time to tumor development
Indicator of tumor development (1=yes, 0=no)
Treatment (1=treated with drug, 0=given placebo)
Klein and Moeschberger (1997) Survival Analysis Techniques for Censored
and truncated data, Springer.
Dataset imported from https://www.r-project.org.