The rats data set in the survival package in R can be loaded by typing "data(rats)". It contains data on 300 rats-3 selected from each of 100 litters-that were followed for tumor incidence. The variable time is the follow-up times and the variable status is the event indicator.
- How many rats had tumors? What was the total rat-time contributed by all the animals? What was the incidence rate for tumors?
- Calculate a Wald 95% confidence interval for the true incidence rate λ
(which is also the exponential rate parameter and hazard).